Mercedes Cosworth- Webers or ITB's?
Discussion
Hey all, I'm prepping a Mercedes 2.5-16v for racing, I'll be mildly modifying the head etc, and fitting lumpy cams which should take the red line to around 8500RPM. I'm hoping to make around 250bhp, but my main decision is whether to go with twin Weber DCOE 50's or Jenvey ITB's and efi.
I've never messed around with EFI before and the thought of a single low pressure fuel pump, single fuel line, and a pair of carbs is so much more appealing than having to install twin lines, high pressure pump(s), more relays, sensors and tonnes of wiring. If the Webers give 95% of the EFI potential then I'm sold, but I'd really appreciate some input from others on this.
By the way I'm removing the standard mechanical injection and also replacing the standard ignition side, most likely with EDIS.
Cheers,
TC
I've never messed around with EFI before and the thought of a single low pressure fuel pump, single fuel line, and a pair of carbs is so much more appealing than having to install twin lines, high pressure pump(s), more relays, sensors and tonnes of wiring. If the Webers give 95% of the EFI potential then I'm sold, but I'd really appreciate some input from others on this.
By the way I'm removing the standard mechanical injection and also replacing the standard ignition side, most likely with EDIS.
Cheers,
TC
What injection system was in place ? Surely there is already a high pressure electric pump and lines fitted ?
The car isnt so old it would have used a 100% mechanical system ?
If it's race only and lower rpm's dont matter at all, then no doubt the carbs will work fine. Mapped ignition would still be worth doing though.
But proper efi would just be better all round
The car isnt so old it would have used a 100% mechanical system ?
If it's race only and lower rpm's dont matter at all, then no doubt the carbs will work fine. Mapped ignition would still be worth doing though.
But proper efi would just be better all round
Hi Stevie, I'm not sure what pump it has but as it's 26 years old I'd want to replace it anyway, and I'll be replacing the fuel tank so the lines will be new too (I know one extra line isn't exactly a nuisance).
I know people say carbs go out of tune but the thought of having them set up in a morning makes it really tempting, I'd expect to have to do a couple of track days to continuously tweek an EFI set up, although this is probably the case with setting up a carb perfectly too! I was thinking of a wideband lambda and gauge as I did in my V8 MX5 so I can monitor the AFR when driving, just for peace of mind and getting close with setting up?
I know people say carbs go out of tune but the thought of having them set up in a morning makes it really tempting, I'd expect to have to do a couple of track days to continuously tweek an EFI set up, although this is probably the case with setting up a carb perfectly too! I was thinking of a wideband lambda and gauge as I did in my V8 MX5 so I can monitor the AFR when driving, just for peace of mind and getting close with setting up?
I believe they had Bosch K Jetronic.
I would go for EFI. With carbs, you will still need to find a mappable ignition solution, which would need an engine speed sensor and a load sensor, be that TPS or MAP. Keeping it simple batch fire EFI with wasted spark ignition you would need, Eng speed, TPS, Inlet air temp and coolant temp sensors, ITBs, injectors, fuel rail, fuel pump and wiring. Finding suitable ITBs would be the hardest thing in the UK.
Only 250hp from a 2.5 at 8500rpm is a little pessimistic IMO, given a stock Merc Cosworth 2.5 Evo makes 235 at 7200rpm with cats.
Head work, mild cams and a compression bump along with ITBs should see 260hp+ and 7500rpm. If you want to make power at 8500rpm, you will need some serious cam duration and corresponding bottom end strengthening to cope, but should be nudging 300hp.
I would go for EFI. With carbs, you will still need to find a mappable ignition solution, which would need an engine speed sensor and a load sensor, be that TPS or MAP. Keeping it simple batch fire EFI with wasted spark ignition you would need, Eng speed, TPS, Inlet air temp and coolant temp sensors, ITBs, injectors, fuel rail, fuel pump and wiring. Finding suitable ITBs would be the hardest thing in the UK.
Only 250hp from a 2.5 at 8500rpm is a little pessimistic IMO, given a stock Merc Cosworth 2.5 Evo makes 235 at 7200rpm with cats.
Head work, mild cams and a compression bump along with ITBs should see 260hp+ and 7500rpm. If you want to make power at 8500rpm, you will need some serious cam duration and corresponding bottom end strengthening to cope, but should be nudging 300hp.
Hey other Steve, thanks for the input, yes it currently has K Jet which is not in tune, nor is the ignition.
I'm coming round to the the idea of injection now, I've had a chat with the nice guys at AT Power who will sell me a lovely set of DCOE pattern ITB's, they seem to have a good reputation for their spindle-free ITB's which flow very well in tests. They work regularly with Emerald (re the ECU) although after a little research I think I may go down the OMEX 600 route.
I'm secretly hoping to hit around 270bhp but not sure I'll do it given the stock heads are already flowed quite well and have decent manifolds as standard, it also has forged pistons as standard and the bottom end has a good reputation, although I may be able to lose some recip weight in the con rods and flywheel which would help it rev better. The CAT cams that I've been quoted for will move the power up to around 8500rpm, I don't want to go berserk as I've got to be able to afford to run it!
I've got a single Weber DCOE going on my rally spec (classic) mini, I'll have to keep that as my time warp car and get my induction roar hit from that!
I'm coming round to the the idea of injection now, I've had a chat with the nice guys at AT Power who will sell me a lovely set of DCOE pattern ITB's, they seem to have a good reputation for their spindle-free ITB's which flow very well in tests. They work regularly with Emerald (re the ECU) although after a little research I think I may go down the OMEX 600 route.
I'm secretly hoping to hit around 270bhp but not sure I'll do it given the stock heads are already flowed quite well and have decent manifolds as standard, it also has forged pistons as standard and the bottom end has a good reputation, although I may be able to lose some recip weight in the con rods and flywheel which would help it rev better. The CAT cams that I've been quoted for will move the power up to around 8500rpm, I don't want to go berserk as I've got to be able to afford to run it!
I've got a single Weber DCOE going on my rally spec (classic) mini, I'll have to keep that as my time warp car and get my induction roar hit from that!
topcat1 said:
They work regularly with Emerald (re the ECU) although after a little research I think I may go down the OMEX 600 route.
I remember friends with Westfields being very upset a few years ago that their Omex ECUs were locked and they weren't able to access the calibrations without using an Omex approved installer. No idea if this still happens but worth checking. Emerald is open and you can do what you like.
Even making 270hp at 8500rpm is a low state of tune. If a stock engine is making 70lbft/litre at 7200, 270 @ 8500 is 68lbft/litre. No better, just turning faster.
To give you an indication, my BMW S14 2.5, with head work, upped compression 292/284 cams ITBs and Efi makes 275hp at 7500rpm and 200lbft at 6600 with a usable torque range of 3200-7700rpm.
I think a stock engine with ITBs and well mapped EFI would make pretty close to 250hp.
To give you an indication, my BMW S14 2.5, with head work, upped compression 292/284 cams ITBs and Efi makes 275hp at 7500rpm and 200lbft at 6600 with a usable torque range of 3200-7700rpm.
I think a stock engine with ITBs and well mapped EFI would make pretty close to 250hp.
Give Thorsten Stadler a call, what he doesn't know about these cars isn't worth knowing.
http://www.190teile.de/
http://www.190teile.de/
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