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Re: #BHP vs MPG
[Re: djmobi]
#809135
07/04/2009 13:15
07/04/2009 13:15
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Joined: Dec 2005
Posts: 882 Banbury
djmobi
OP
Enjoying the ride
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OP
Enjoying the ride
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Posts: 882
Banbury
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I hve had a good read through the tuning guides for the 20VT and was wondering if there are certain mods you can do that effect MPG less than others or is it a case of the higher the BHP the lower the MPG???
Back Owning a Coupe
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Re: #BHP vs MPG
[Re: djmobi]
#809136
07/04/2009 13:15
07/04/2009 13:15
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Dan_S
Unregistered
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Dan_S
Unregistered
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?! i think something is missing... .
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Re: #BHP vs MPG
[Re: ]
#809138
07/04/2009 13:16
07/04/2009 13:16
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TurboJ
Unregistered
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TurboJ
Unregistered
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here comes Nigel.....
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Re: #BHP vs MPG
[Re: ]
#809139
07/04/2009 13:16
07/04/2009 13:16
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Dan_S
Unregistered
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Dan_S
Unregistered
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the basic ones like air filter and exhaust will not affect the mpg much
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Re: #BHP vs MPG
[Re: djmobi]
#809140
07/04/2009 13:17
07/04/2009 13:17
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JIM16vt
Unregistered
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JIM16vt
Unregistered
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Depends what car mate, in my diesel runaround it has to be MPG.
But in my modded quick coupe mpg is not in my head, i'm just think BHP.
Coupe isn't really a MPG car, MPG is more of a diesel thing or petrol 1.1. Deffo not acoupe anyway, all tho a standard coupe is not that bad off boost and drove sensible.
Hello mate, werlcome to the forum.
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Re: #BHP vs MPG
[Re: OO7]
#809150
07/04/2009 13:38
07/04/2009 13:38
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eldinho
Unregistered
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eldinho
Unregistered
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you should only really notice big mpg differences when you are accelerating hard, with normal driving it should be quite similar (better if you have headwork). But like J says I'll let Nigel have his moment
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Re: #BHP vs MPG
[Re: ]
#809159
07/04/2009 14:03
07/04/2009 14:03
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Joined: Dec 2005
Posts: 3,158 Near Reading
JohnS
I need some sleep
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I need some sleep
Joined: Dec 2005
Posts: 3,158
Near Reading
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If you drive it economically as long as the modifications are well thought out there will be little or no effect on MPG. Tuning the ECU will actually improve like for like steady running as more ignition advance improves the combustion of fuel.
Anything that reduces the impedance of airflow into or out of the engine will generally improve economy.
Former low boost hero - 616BHP@1.5 bar. 2.4 20VT RIP
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Re: #BHP vs MPG
[Re: djmobi]
#809166
07/04/2009 14:10
07/04/2009 14:10
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Squid
Unregistered
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Squid
Unregistered
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If there was ever a topic that was made for Nigel, this is it. He's probably composing a 2000 word essay as I write this....
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Re: #BHP vs MPG
[Re: ]
#809181
07/04/2009 14:31
07/04/2009 14:31
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DanielTheManual
Unregistered
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DanielTheManual
Unregistered
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Yes, almost certainly quoting his best tank range efforts on that 1 historic (but dull) drive
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Re: #BHP vs MPG
[Re: ]
#809199
07/04/2009 14:54
07/04/2009 14:54
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peanuthead
Unregistered
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peanuthead
Unregistered
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i am trying to work out how long it would take to recop the cost of a 400bhp coversion if i got another 10mpg as nigel gets between 35 and 42mpg and i get between 25 and 30mpg. i do 15000 miles a year so not to long lol :-)
my caluclations as a 10mpg difference i would make back about £790 a year. how much would it cost to hit 400bhp?
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Re: #BHP vs MPG
[Re: ]
#809204
07/04/2009 14:59
07/04/2009 14:59
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Joined: Dec 2005
Posts: 882 Banbury
djmobi
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Enjoying the ride
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OP
Enjoying the ride
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Posts: 882
Banbury
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Sounds like good news then.......mod as much as you want and you could even potentially improve MPG.
Back Owning a Coupe
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Re: #BHP vs MPG
[Re: djmobi]
#809210
07/04/2009 15:05
07/04/2009 15:05
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peanuthead
Unregistered
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peanuthead
Unregistered
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well the main thing is increasing the mpg on these or any car is having a decent port and polished head, decent balanced engine using low resistance parts and most of all a good map.
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Re: #BHP vs MPG
[Re: ]
#809212
07/04/2009 15:07
07/04/2009 15:07
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Joined: Dec 2005
Posts: 882 Banbury
djmobi
OP
Enjoying the ride
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OP
Enjoying the ride
Joined: Dec 2005
Posts: 882
Banbury
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If you do the air filter and exhaust do you get much of a BHP increase?
Back Owning a Coupe
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Re: #BHP vs MPG
[Re: ]
#809222
07/04/2009 15:13
07/04/2009 15:13
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Squid
Unregistered
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Squid
Unregistered
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If you are looking to modify a Coupe engine on the basis of saving money on fuel, well... That's just Once you go above 350bhp you will require a complete engine rebuild. That will cost about £1200 in forged parts alone and that's before you start on the ancilaries like bearings, gaskets, etc, etc. Then you have labour on top of that, bigger turbo, FMIC, exhaust etc. It really is an expensive and time consuming business not to be undertaken lightly. if you are on a budjet, don't do it, as there is always something else to do. The best bet is to take a look at TurboJ's 20VT tuning guide, and make a decision after reading that. Also, don't forget that if you modify a car to give it improved performance, yes, it will improve MPG if you drive it cautiously, but who is going to drive a 300+bhp coupe like an OAP? You are bound to take it out for a good thrashing every now and again, that is what the car is for! If you want to save money, buy an economical diesel run around.
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Re: #BHP vs MPG
[Re: OO7]
#809241
07/04/2009 15:39
07/04/2009 15:39
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JIM16vt
Unregistered
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JIM16vt
Unregistered
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007 it surprises me because when I modded my bravo hgt the fuel comsumption went rediculously high. I couldn't belive it. havn't noticed it yet with coupe but my project has a long way to go so i expect it will soon.
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Re: #BHP vs MPG
[Re: OO7]
#809282
07/04/2009 16:09
07/04/2009 16:09
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Joined: Dec 2005
Posts: 3,158 Near Reading
JohnS
I need some sleep
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I need some sleep
Joined: Dec 2005
Posts: 3,158
Near Reading
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Buy a 60MPG+ car and spend the savings on tuning your coupe Based on business miles that I get paid at the gov rate I realised that by running a 60MPG car instead of a 30MPG car for my 35000 business miles/year I could save a few grand a year in total car expenditure. So now I use a Audi A2 TDI for work. £35 a year to road tax, £200 to insure and does 62MPG without much effort. Takes 25,000 miles to wear out the tyres and is made from lightweight aluminium so will never rust. Helps pay the insurance and road tax on my other 4 cars that I get my fun from!!
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Re: #BHP vs MPG
[Re: JohnS]
#809285
07/04/2009 16:15
07/04/2009 16:15
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peanuthead
Unregistered
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peanuthead
Unregistered
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yeah but i only use my car to drive for pleasure not work and i do 50/50 motorway and late night b roads so i normally cruise on the motorway which would give me great mpg and then have 400bhp tp have fun with on the way home :-)
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Re: #BHP vs MPG
[Re: ]
#809286
07/04/2009 16:16
07/04/2009 16:16
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peanuthead
Unregistered
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peanuthead
Unregistered
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i never said it was the best cost effective method but atleast it would be fun as i don't just want a car i drag out the garage on a sunny day and driving a boring car most the time as whats the point,
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Re: #BHP vs MPG
[Re: ]
#809377
07/04/2009 18:08
07/04/2009 18:08
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Trickymex
Unregistered
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Trickymex
Unregistered
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rule number one of engine tuning is the more fuel and air an engine can consume the more power it will produce
Obviously there are other factors that effect fuel consumption, these are effiencys like thermal effiency, mechanical effiency, we will ignor these as they are not going to be very different from one 20vt to another 20vt although things like wheel diamiter can effect these
Ontop of this and as john has said how it was mapped can effect it also
But you will find with turbo charged engine that have larger turbos fitted they will be laggy in comparison to the standard setup, this means they will be producing boost later in the rev range than the standard setup, in some cases this can be higher than your cruising speed on the motorway
So if you sit at 70mph and 3000rpm you may, depending on your setup be producing very little boost and as such you will not require so much fuel.
So if your clever with your setup you can make a very powerfull car but also in a certain situation very economical
Ricky
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Re: #BHP vs MPG
[Re: Flea]
#809424
07/04/2009 19:11
07/04/2009 19:11
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Trickymex
Unregistered
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Trickymex
Unregistered
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Thank you Flea, I did not make that very clear and that in itself makes clear that driving style makes a massive difference to fuel consumption
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Re: #BHP vs MPG
[Re: ]
#809489
07/04/2009 20:22
07/04/2009 20:22
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Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
Forum veteran
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Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
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LOL - am I getting THAT predictable? The best mods you can do for performance AND better mpg is headwork The cylinder head is the most restrictive part of the engine and any gains here will always result in better flow (which equals better power and/or better mpg I'm running around 400bhp and I have got a best of 43mpg. However, when I got the 43mpg, I doubt that I produced more than 40bhp all day. I can get mid to high 30's mpg cruising at motorway speeds. Even my daily commute gets me 30mpg if I turn the boost down. I conservatively reckon that when I'm producing peak power, I'm probably doing 6 or 7 mpg at best. I once got 7.9mpg while on track (and that was with 300bhp) A lot depends on the mapping too - Flea currently has my car for some more tweaks and I'm hoping he'll keep it fairly lean off boost so I can get decent mpg on long motorway journeys. So - spend £1000 on a mildly-worked cylinder head and get an extra 30 - 50 miles per tank - it won't be long before its paid for itself
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Re: #BHP vs MPG
[Re: Nigel]
#809555
07/04/2009 21:35
07/04/2009 21:35
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TurboJ
Unregistered
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TurboJ
Unregistered
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it won't be long before its paid for itself Yea and the rest
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Re: #BHP vs MPG
[Re: ]
#809783
08/04/2009 09:39
08/04/2009 09:39
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peanuthead
Unregistered
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peanuthead
Unregistered
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£1000 for a modified head is a lot of money! how come its so expensive on these cars as any other head i have had port polished and larger valves and so on has worked out about £450-550 but then thats with me fitting it.
i recon that if you picked up very good hardly used secondand parts and built it up then 400bhp could be done for about £3000 if i done all the work except mapping. so it would take about 2.5 years to pay off in better fuel consumption but more relisticly you would maybe lose 2k in extra mapping and parts failing but then that would be a fun 2k.
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Re: #BHP vs MPG
[Re: ]
#809790
08/04/2009 09:52
08/04/2009 09:52
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Joined: Dec 2005
Posts: 12,295 Sandhurst
Begbie
Ex El Presidente
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Ex El Presidente
I AM a Coop
Joined: Dec 2005
Posts: 12,295
Sandhurst
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how come its so expensive on these cars as any other head i have had port polished and larger valves and so on has worked out about £450-550 but then thats with me fitting it. Do you get any flow results with the head? A properly modified head will easily cost in excess of £2000+, there is a lot of work to be done, especially when you are watching how the airflow goes through the head, matching the inlet / exhaust ratio to keep it around 75% or 85% (can't remember), lapping, grinding, modifying the seat, fitting race spec valve guides, cleaning everything
Your car is Usain Bolt with wellies
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Re: #BHP vs MPG
[Re: Begbie]
#809802
08/04/2009 10:01
08/04/2009 10:01
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peanuthead
Unregistered
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peanuthead
Unregistered
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maybe i am used to old school engines as i used to know a guy who used to work for vulcan and he done all my head work for me. and most the old school guys i used charged around £450 or a 4 pot 8 vlave £550 for a 4 pot 16v and £600 or a straight six. i am not saying it is easy work but the haed for my old 2.1 pinto that made 212bhp cost me £300 to get sorted lol. might see what these guys can do for coop heads as they are very good at what they do.
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Re: #BHP vs MPG
[Re: ]
#809821
08/04/2009 10:13
08/04/2009 10:13
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eldinho
Unregistered
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eldinho
Unregistered
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i recon that if you picked up very good hardly used secondand parts and built it up then 400bhp could be done for about £3000 if i done all the work except mapping. all I can say to that is dream on!
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Re: #BHP vs MPG
[Re: ]
#809833
08/04/2009 10:19
08/04/2009 10:19
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eldinho
Unregistered
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eldinho
Unregistered
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I've spent easily over that on parts alone to get it from 360-370bhp to hopefully 400+! When I bought the car off Joe I worked out that he had spent close to £15k. Tuning isn't cheap!
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Re: #BHP vs MPG
[Re: ]
#809838
08/04/2009 10:21
08/04/2009 10:21
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peanuthead
Unregistered
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peanuthead
Unregistered
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really? i think i might give up on the coop then as pretty much any other turbo car i ahve had i could get 400 bhp for around £3000 to £3500 using secondhand parts.
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Re: #BHP vs MPG
[Re: ]
#809844
08/04/2009 10:28
08/04/2009 10:28
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eldinho
Unregistered
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eldinho
Unregistered
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it wouldn't cost nowhere near what has been spent on mine, but I think you are looking at least double what you've said to have a "reliable" 400bhp. And thats without suspension and brakes.
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Re: #BHP vs MPG
[Re: ]
#809852
08/04/2009 10:38
08/04/2009 10:38
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Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
Forum veteran
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Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
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This has been done a thousand times, but let's do it once more with secondhand parts prices
Rods - £500 Pistons - £500 Flowed head - £500 Turbo - £750 Downpipe - £200 Boost control - £250 Intake (filter, SIP) £100 Intercooler - £300 Dumpvalve - £50 injectors - £200 Mapping - £500
Total = £3,850
This assumes you can actually FIND all the parts secondhand - you may end up with a very long wait.
It also assumes you fit everything yourself - it doesn't include all the extras (would you fit a flowed head without replacing the cambelt? - no, neither would I)
I reckon this is the absolute minimum you would need to get to 400bhp - however, IMHO, you would also need to spend another £1000 or so on making the car stop and handle as well.
To do it properly and with someone fitting bits for you, I still reckon you're looking at £7,500 minimum
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Re: #BHP vs MPG
[Re: Nigel]
#809862
08/04/2009 10:48
08/04/2009 10:48
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eldinho
Unregistered
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eldinho
Unregistered
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Those bits that Nigel mentioned like cambelts soon add up! rebore, gasket set, spark plugs, bearings, the list goes on. Nigel can I shop where you do for cylinder heads please
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Re: #BHP vs MPG
[Re: ]
#809870
08/04/2009 10:56
08/04/2009 10:56
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peanuthead
Unregistered
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peanuthead
Unregistered
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yeah you could get 400bhp using secondhand parts on a tomcat. infact there was a full setup including new forge block bored to 2.1 and so on for 2k including turbo rated to 380bhp for 2k on rovercoupe forum. so maybe 400bhp would be achivable on the tomcat. well maybesay 4k if i done the work myself on the coop. using secondhand parts a gtst would be about 3k and a rb26 gtr even less. i have some of that list waiting to go one or already on so im getting there :-) i agree with the handdling and brakes but thats another story. i know one guy with 610bhp on a certain car and he had standard carpy brakes. he was happy with it but then he is a nutter lol
Last edited by peanuthead; 08/04/2009 10:57.
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Re: #BHP vs MPG
[Re: ]
#809877
08/04/2009 11:06
08/04/2009 11:06
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peanuthead
Unregistered
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peanuthead
Unregistered
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i recon acttully 4.5k with the bits and you would be in there with a uprated clutch and so on. to be fair though 400bhp coop should be worthn the money and be very quick.
also i recon that you would driven day to day achive 10mpg better than you would at 340bhp and the difference is price on parts is maore due to a rebuild but that coule be recouped.
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Re: #BHP vs MPG
[Re: JohnS]
#809961
08/04/2009 12:28
08/04/2009 12:28
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JIM16vt
Unregistered
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JIM16vt
Unregistered
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Me too, coupe for bhp and fun
turbo diesel run around for mpg and genral running around in confort and economal movement.
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Re: #BHP vs MPG
[Re: ]
#809965
08/04/2009 12:32
08/04/2009 12:32
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peanuthead
Unregistered
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peanuthead
Unregistered
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well i just think that unless i get really rich then i want one car that does it all and a coop that could get 35-40mpg driving carfully but has the neck breaking power when putting my foot down would be ideal.
out of intrest if i went from 300bhp to 400bhp i doubt any parts really are interchangable so i was just going to save and go for the 400bhp from the off or do you think its worth hit 300bhp first?
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Re: #BHP vs MPG
[Re: ]
#809974
08/04/2009 12:41
08/04/2009 12:41
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eldinho
Unregistered
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eldinho
Unregistered
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most of the parts you are going to use getting 300bhp will still be used getting 400bhp. The only things that you won't are the turbo and the map. Just go for a downpipe which fits onto a GT series turbo and also a clutch which will support 400bhp (I know clutches are rated to torque ) 300bhp GT28R FMIC Full Exhaust Walbro Fuel Pump with wiring mod SIP with Filter EBC Dumpvalve Some sort of map/chip 400bhp GT**** Rods Pistons Flowed head Larger injectors Bigger MAF Maybe Cams?? Remap
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Re: #BHP vs MPG
[Re: ]
#809990
08/04/2009 12:58
08/04/2009 12:58
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peanuthead
Unregistered
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peanuthead
Unregistered
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another idea would be to install a gt30r say for 400bhp and the fmic, down pipe, full exhaust,welbro fuel pump,sipand map it on a low boost setting and deal with slightly more lag and then build the engine up and add the forged bottom end, head, injectors, maf,cams and then get mapper later on?
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Re: #BHP vs MPG
[Re: ]
#809994
08/04/2009 13:08
08/04/2009 13:08
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eldinho
Unregistered
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eldinho
Unregistered
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maybe, but for the little money you are going to lose by the time you have sold the GT28R (presuming you bought it secondhand) I would run a smaller turbo. It won't be much fun having a big turbo with no headwork.
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Re: #BHP vs MPG
[Re: ]
#810007
08/04/2009 13:18
08/04/2009 13:18
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Joined: Dec 2005
Posts: 882 Banbury
djmobi
OP
Enjoying the ride
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OP
Enjoying the ride
Joined: Dec 2005
Posts: 882
Banbury
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Just to set JIM16VT's mind at rest. When I asked the original question I wasnt trying to find out what I can do to improve MPG, I was just wondering if there are certain mods that can improve both BHP and MPG. IMO if you can get the horse power and keep the same MPG or improve it, that makes financial sense for those who cant afford to run 2 cars.
Back Owning a Coupe
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Re: #BHP vs MPG
[Re: djmobi]
#810028
08/04/2009 13:38
08/04/2009 13:38
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JIM16vt
Unregistered
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JIM16vt
Unregistered
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Ok mate, one thing I do know is keeping air filter clean helps. And also just genral looking afterr and maintaing car too.
As for the mods I have always thought that it makes mpg go up, who knows tho.
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Re: #BHP vs MPG
[Re: ]
#810039
08/04/2009 13:53
08/04/2009 13:53
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peanuthead
Unregistered
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peanuthead
Unregistered
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basicly headwork and a decent map will increace mpg and bhp together but head work isn't worth it unless rebulding the bottom end so really just a decent map and keep the car serviced well.
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Re: #BHP vs MPG
[Re: ]
#810139
08/04/2009 16:12
08/04/2009 16:12
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JIM16vt
Unregistered
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JIM16vt
Unregistered
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Supose everyone has there own view and story on how they want there coupe.
IMO, tho there is always going to be a issue with burning MPG in a 2L-turbo
To me it seems crazy talking about trying to save petrol with a engine like that.
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Re: #BHP vs MPG
[Re: ]
#810141
08/04/2009 16:16
08/04/2009 16:16
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peanuthead
Unregistered
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peanuthead
Unregistered
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i know mate i wasn't really being serious. that is just what you tell the missis why you have to get a remap and a bigger turbo lol it will get better mpg but you wouldn't just doing it for that but more the fun factor.
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Re: #BHP vs MPG
[Re: ]
#810731
09/04/2009 12:00
09/04/2009 12:00
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Joined: Dec 2005
Posts: 882 Banbury
djmobi
OP
Enjoying the ride
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OP
Enjoying the ride
Joined: Dec 2005
Posts: 882
Banbury
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I agree with JIM16vt. There is no point buying a 2litre turbo engined car and then worrying about fuel costs, I just want to make sure that when I get mine (Hopefully next month) and start doing some work on it, I dont end up going a bit too far and ending up with a car thats a massive amount of fun, but I can only use it on the weekends because I cant afford to put petrol in the tank.
Back Owning a Coupe
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Re: #BHP vs MPG
[Re: ]
#810748
09/04/2009 12:26
09/04/2009 12:26
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suba
Unregistered
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suba
Unregistered
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Bull - why re-build the bottom end if it does not need it?
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Re: #BHP vs MPG
[Re: djmobi]
#810751
09/04/2009 12:31
09/04/2009 12:31
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suba
Unregistered
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suba
Unregistered
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Why not just get a big V8 then? If you only want one car to do everything and a lot of miles then a turbo gives you the best of both worlds.
I'll sum this up. A flowed head a good map = efficient engine for cruising and more MPG.
However....
High boost and a big turbo mean when you put your foot down MPG will be in single figures, so depending on how you drive I reckon the average is probably about the same. The only exception is if you do a lot of motorway miles.
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Re: #BHP vs MPG
[Re: ]
#810803
09/04/2009 13:23
09/04/2009 13:23
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JIM16vt
Unregistered
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JIM16vt
Unregistered
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Why not get a v8?
For me tubos are much more fun to drive than Nateraly asperarated cars,Not matter how fast they are. Plus it is alot easyer and mcheaper to mod and increase power of a turbo than it is with non-turbo.
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Re: #BHP vs MPG
[Re: ]
#810809
09/04/2009 13:28
09/04/2009 13:28
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suba
Unregistered
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suba
Unregistered
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fine - but they are also better on fuel on a run - so you are onto a winner there!
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Re: #BHP vs MPG
[Re: ]
#810816
09/04/2009 13:37
09/04/2009 13:37
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TurboJ
Unregistered
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TurboJ
Unregistered
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Bull - why re-build the bottom end if it does not need it? Keeps you away from the MRS
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Re: #BHP vs MPG
[Re: ]
#810954
09/04/2009 17:15
09/04/2009 17:15
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JIM16vt
Unregistered
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JIM16vt
Unregistered
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Suba the thing is , a V8 will kill the fuel weather it has 5 liters or eight. Turbo or not engine that size with 24 valves and 6+ cylinder will kill fuel.
Think tho, knowbody who buyes cars with engines like that gives a crap about the mpg.
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