Subaru 2L turbo for rally car
Discussion
I'm after some ECU advice - hope you guys can help.
We're building a Legacy rally car and the donor car was a '94 legacy 2.0L turbo (saloon). As it stands, the engine and ECU are standard (straight out of the road car) but the 'box and final drive are geared differently (4.1 final drive) and the exhaust is a big-bore through to the manifold. The rally car is also
much lighter than the road car (not sure how much though).
So, first question is how well do you think the standard ECU map will work given all the differences above? I guess the big bore will make the turbo spool up differently and the shorter gear ratios will load it up differently and it should pick up revs quicker. I have no idea how "out of tune" the standard ignition and fuel maps will be or if it won't make any difference.
Next question is how much there is to gain by swapping ECUs. The standard map will be set up to balance economy and performance. In this application we can pretty much throw economy out of the window - as long as we stay no more than a litre a mile there will be enough tank capacity to do pretty much any stage we are likely to do in the short term. The budget won't run to a fully mappable Gems system, so if we go for the "chipping" route, will one of the off-the-shelf "chips" suffer the same problems as it's a non-standard set up? Would it need a proper rolling road custom map to make any real improvements?
I *think* the gearing will look much more like an Impreza Ra. Are the ECU's swappable? Hard to believe
I could just swap to an STI ECU and get 280bhp. I'd guess there was something missing that wasn't just swappable the the lagacy engine.
Anyone know how much more grunt the bottom end will take without going to forged bits? I'm assuming the bottom end of the STI motor is built stronger than the standard 2L turbo in the legacy? Obviously I wont need a 100K miles out of it but it will spend a lot of its time howling its head off (not literally I hope) and I'd like a few events out of it before it goes bang!
Sorry for all the questions!
We're building a Legacy rally car and the donor car was a '94 legacy 2.0L turbo (saloon). As it stands, the engine and ECU are standard (straight out of the road car) but the 'box and final drive are geared differently (4.1 final drive) and the exhaust is a big-bore through to the manifold. The rally car is also
much lighter than the road car (not sure how much though).
So, first question is how well do you think the standard ECU map will work given all the differences above? I guess the big bore will make the turbo spool up differently and the shorter gear ratios will load it up differently and it should pick up revs quicker. I have no idea how "out of tune" the standard ignition and fuel maps will be or if it won't make any difference.
Next question is how much there is to gain by swapping ECUs. The standard map will be set up to balance economy and performance. In this application we can pretty much throw economy out of the window - as long as we stay no more than a litre a mile there will be enough tank capacity to do pretty much any stage we are likely to do in the short term. The budget won't run to a fully mappable Gems system, so if we go for the "chipping" route, will one of the off-the-shelf "chips" suffer the same problems as it's a non-standard set up? Would it need a proper rolling road custom map to make any real improvements?
I *think* the gearing will look much more like an Impreza Ra. Are the ECU's swappable? Hard to believe
I could just swap to an STI ECU and get 280bhp. I'd guess there was something missing that wasn't just swappable the the lagacy engine.
Anyone know how much more grunt the bottom end will take without going to forged bits? I'm assuming the bottom end of the STI motor is built stronger than the standard 2L turbo in the legacy? Obviously I wont need a 100K miles out of it but it will spend a lot of its time howling its head off (not literally I hope) and I'd like a few events out of it before it goes bang!
Sorry for all the questions!
The std ecu will work fine.
Swapping ecu's from car to car can sometimes give benefits, somtimes it will make it worse.
there arent any "off the shelf" chips as such for that year, although some guys did develop a new board, which allowed the fitment of som eproms, that they could re-program. It was relatively cheap, but I think they are no longer available.
Cheapest option would be to buy a Link ecu, or an Apexi PFC
Gains depend entirely on what you want. But std turbo fitted to the legacy etc would limit power to about 250bhp or so, regardless of other mods.
STI bottom end is no different to a Legacy, apart from stronger pistons.
Legacy heads are different, and Impreza heads are better, but if you fit these to a Legacy bottom end, they will also raise the compression.
Get a turbo, ecu, fuel pump and injectors, and you will easily see over 300bhp when properly mapped.
Ask here also, and you will get any info and advice you need.
http://bbs.22b.com/cgi-bin/ultimatebb.cgi
You could also ask on Scoobynet, but there are so many tossers there too, its hard to know who to listen to.
Where in the country are you ?
Swapping ecu's from car to car can sometimes give benefits, somtimes it will make it worse.
there arent any "off the shelf" chips as such for that year, although some guys did develop a new board, which allowed the fitment of som eproms, that they could re-program. It was relatively cheap, but I think they are no longer available.
Cheapest option would be to buy a Link ecu, or an Apexi PFC
Gains depend entirely on what you want. But std turbo fitted to the legacy etc would limit power to about 250bhp or so, regardless of other mods.
STI bottom end is no different to a Legacy, apart from stronger pistons.
Legacy heads are different, and Impreza heads are better, but if you fit these to a Legacy bottom end, they will also raise the compression.
Get a turbo, ecu, fuel pump and injectors, and you will easily see over 300bhp when properly mapped.
Ask here also, and you will get any info and advice you need.
http://bbs.22b.com/cgi-bin/ultimatebb.cgi
You could also ask on Scoobynet, but there are so many tossers there too, its hard to know who to listen to.
Where in the country are you ?
Thanks for the info Stevie - most useful, and good to know the std ecu will run OK.
When you say there are no off-the-shelf chips, do you mean that year isn't chippable? Had the lid off the ECU and there is a big empty socket that looks like it would take an EPROM but could be for anything. Had a wildly optimistic thought that if it was for an eprom and you shorted a link on the board to get it to use the alternative map, then you could make the link switchable on the dash and get a switchable road section/stage mapping for free! Sounds too good to be true though!
We're probably going to stick to standard bits on the engine itself for the time being (budget etc) although we're going to use a bigger fuel pump if only to stop it leaning out at high revs. I was just wondering if I could trade off any fuel economy that I dont need for a bit of extra low end grunt just by playing with the ecu maps. Guess the answer if no if its not re-mappable though!
I'm in Silverstone BTW.
When you say there are no off-the-shelf chips, do you mean that year isn't chippable? Had the lid off the ECU and there is a big empty socket that looks like it would take an EPROM but could be for anything. Had a wildly optimistic thought that if it was for an eprom and you shorted a link on the board to get it to use the alternative map, then you could make the link switchable on the dash and get a switchable road section/stage mapping for free! Sounds too good to be true though!
We're probably going to stick to standard bits on the engine itself for the time being (budget etc) although we're going to use a bigger fuel pump if only to stop it leaning out at high revs. I was just wondering if I could trade off any fuel economy that I dont need for a bit of extra low end grunt just by playing with the ecu maps. Guess the answer if no if its not re-mappable though!
I'm in Silverstone BTW.
What you seen is correct, and is how the "Scoobyecu" project worked.
But as I said, this was a something some guys developed themselves, and not really a commercial thing. The plug in board, is no longer available as far as i know. They sourced the eproms, the board, and wrote the code to allow them to make changes.
It was just handy that Subaru left this socket and jumper in the factory ecu.
If you contact Pavlo on 22b.com, he knows all about the Scoobyecu project, as I think he was involved in its development, and will also be able to help you with any upgrades.
or you can get him on paul at zenperformance.co.uk He's in the Wellingborough area.
Obviously do the paul@zen.....
Computer bots sometimes grab peoples emails from forums and send spam/virus', so dont like typing them in full in public.
But as I said, this was a something some guys developed themselves, and not really a commercial thing. The plug in board, is no longer available as far as i know. They sourced the eproms, the board, and wrote the code to allow them to make changes.
It was just handy that Subaru left this socket and jumper in the factory ecu.
If you contact Pavlo on 22b.com, he knows all about the Scoobyecu project, as I think he was involved in its development, and will also be able to help you with any upgrades.
or you can get him on paul at zenperformance.co.uk He's in the Wellingborough area.
Obviously do the paul@zen.....
Computer bots sometimes grab peoples emails from forums and send spam/virus', so dont like typing them in full in public.
I would have thought going programmable via something like megasquirt would be a good goer, then get the thing set up to produce proper power. Get your ignition right on the edge with 98 fuel, I also think you can set up boost retard which would be of benefit if you're running adjustable boost.
I personally don't like things where the setup is left to someone with skills beyond mine. I dislike injection but if I had no choice, I would run a fully programmable one.
I personally don't like things where the setup is left to someone with skills beyond mine. I dislike injection but if I had no choice, I would run a fully programmable one.
You can buy both Link, and Apexi ecu's for sensible money, and they plug straight in. I wouldnt be bothered with the hassle of trying to wire, and sort triggers for a different ecu.
And anyone who would even consider ditching the efi on such an engine is well and truly mental.
IMO subarus are awesome engines, and can make some serious power.
There are already several 10 sec 1/4 mile runners, that can be driven daily like a normal car, and can still return 30mpg on a run.
Thats better economy than a standard car.
If you are really budget limited, get the ecu, and get a better turbocharger. The VF12 thats on oyurs, is pretty small. If you can source a TD05 from an early wrx, and convert it to front entry ( early TD05's have a 90deg elbow as normal )
You then have pretty fast spooling, 350bhp capable turbocharger. get a walbro pump, and some injectors, and if the bottom end holds together, which it should do for a while even std, and your laughing.
At 300bhp it should last a very long time if tuned properly.
And anyone who would even consider ditching the efi on such an engine is well and truly mental.
IMO subarus are awesome engines, and can make some serious power.
There are already several 10 sec 1/4 mile runners, that can be driven daily like a normal car, and can still return 30mpg on a run.
Thats better economy than a standard car.
If you are really budget limited, get the ecu, and get a better turbocharger. The VF12 thats on oyurs, is pretty small. If you can source a TD05 from an early wrx, and convert it to front entry ( early TD05's have a 90deg elbow as normal )
You then have pretty fast spooling, 350bhp capable turbocharger. get a walbro pump, and some injectors, and if the bottom end holds together, which it should do for a while even std, and your laughing.
At 300bhp it should last a very long time if tuned properly.
I dont think thats correct.
Restrictor or not, a 300bhp capable turbo will never be able to flow more air than 300bhp.
So with enough boost mid-range etc you may still be able to achieve 300bhp, with massive torque.
If you only had a 200bhp capable turbo, then restrictor or not, the turbo is the limiting factor.
Rallycross cars use a small restrcitor too, but they dont run small turbos.
The turbo needs to be suitably sized for the power/torque you want regardless of any restrictor used.
Restrictor or not, a 300bhp capable turbo will never be able to flow more air than 300bhp.
So with enough boost mid-range etc you may still be able to achieve 300bhp, with massive torque.
If you only had a 200bhp capable turbo, then restrictor or not, the turbo is the limiting factor.
Rallycross cars use a small restrcitor too, but they dont run small turbos.
The turbo needs to be suitably sized for the power/torque you want regardless of any restrictor used.
stevieturbo said:
I dont think thats correct.
Restrictor or not, a 300bhp capable turbo will never be able to flow more air than 300bhp.
So with enough boost mid-range etc you may still be able to achieve 300bhp, with massive torque.
If you only had a 200bhp capable turbo, then restrictor or not, the turbo is the limiting factor.
Rallycross cars use a small restrcitor too, but they dont run small turbos.
The turbo needs to be suitably sized for the power/torque you want regardless of any restrictor used.
To get that midrange torque would require a lot of development. Whats the point in using a turbo that can produce boost for 350bhp if the restrictor brings it down to 300? you can opt for a smaller turbo that can produce its maximum unrestricted power and then gain in low-midrange performance with reduced lag. The idea of the restrictor is to 'restrict' maximum power so why try to get 300bhp at 6000 rpm and 300lb/ft from 3500 upwards when you can get 300bhp at 5000rpm with 400 lb/ft from 2500 upwards? (all figures are wild guestimates for comparison purposes
) But there is a lot more to it than sticking a different turbo on it, camshaft selection and compresion ratio also play a big part in the business of producing max midrange torque to make the most of a restricted engine.
I am going to be playing with a Spec C shortly on Motec M800 with a 32mm Grp N restrictor so should be fun
I appreciate that, i was just getting the point across that using a bigger turbo to gain power on a restricted engine is pointless if a smaller turbo will give bigger improvements elsewhere for a rallycar in a point to point situation. 
Back to the original reason for this thread, then all points made already are valid, but dont forget an engine that hasnt been setup correctly for the conditions it is used in will end up with a very expensive rebuild. If you can afford the likes of a knock sensor and Air/Fuel ratio monitor to keep an eye on things then the likelyhood of a meltdown can be minimised. If you can afford a remap of some sort do it. a rallycar is constantly on the boil, it will be at the top of its stress levels for a long time, it wont be doing constant high speeds for airflow for cooling so it will be susepticle to harsh heat conditions. do the best you can to take care of it, a £500 setup could be cheaper than a £2000 rebuild after your first event.
>> Edited by Mikey G on Friday 29th July 20:52
Back to the original reason for this thread, then all points made already are valid, but dont forget an engine that hasnt been setup correctly for the conditions it is used in will end up with a very expensive rebuild. If you can afford the likes of a knock sensor and Air/Fuel ratio monitor to keep an eye on things then the likelyhood of a meltdown can be minimised. If you can afford a remap of some sort do it. a rallycar is constantly on the boil, it will be at the top of its stress levels for a long time, it wont be doing constant high speeds for airflow for cooling so it will be susepticle to harsh heat conditions. do the best you can to take care of it, a £500 setup could be cheaper than a £2000 rebuild after your first event.
>> Edited by Mikey G on Friday 29th July 20:52
Guys, thanks for the info.
You are right - the budget is somewhat limited! (Isn't it always?) In the short term I think the quicker stage times will come from making it stop and handle better (and getting the driver more experience!) so the initial upgrade budget will go on that rather than going too aggressive on the motor. My initial concern was how well the road car engine was going to do when transplanted into the rally car (different gearing/exhaust/restrictor etc).
My thinking was more along the lines of getting back any performance lost by running it in a different environment rather than making any big gains over what it had originally, if that makes any sense. I know vaguely what goes on in the ECU, but not enough to know how much effect things like weight/gearing have on it. (A little knowledge is a dangerous thing!) If a re-map would make the most of the current set-up then it would be worth doing.
Mikey - that's a good point - a remap to set it up correctly may lengthen its life rather than shorten it! Do the standard ECU's already use a knock sensor? I'd think any mapping that increased boost would need it as a safety margin. Actually, do you know if the standard ECU is adaptive? If I tip in optimax with a load of octane booster (or even Av-gas) would it adapt the timing to take advantage over 95-unleaded? Would it need a Link or Apexi ECU to make use of an air/fuel monitor?
Sorry for yet more questions!
Cheers!
You are right - the budget is somewhat limited! (Isn't it always?
) In the short term I think the quicker stage times will come from making it stop and handle better (and getting the driver more experience!) so the initial upgrade budget will go on that rather than going too aggressive on the motor. My initial concern was how well the road car engine was going to do when transplanted into the rally car (different gearing/exhaust/restrictor etc). My thinking was more along the lines of getting back any performance lost by running it in a different environment rather than making any big gains over what it had originally, if that makes any sense. I know vaguely what goes on in the ECU, but not enough to know how much effect things like weight/gearing have on it. (A little knowledge is a dangerous thing!) If a re-map would make the most of the current set-up then it would be worth doing.
Mikey - that's a good point - a remap to set it up correctly may lengthen its life rather than shorten it! Do the standard ECU's already use a knock sensor? I'd think any mapping that increased boost would need it as a safety margin. Actually, do you know if the standard ECU is adaptive? If I tip in optimax with a load of octane booster (or even Av-gas
) would it adapt the timing to take advantage over 95-unleaded? Would it need a Link or Apexi ECU to make use of an air/fuel monitor? Sorry for yet more questions!
Cheers!
lightspeed said:
Mikey - that's a good point - a remap to set it up correctly may lengthen its life rather than shorten it! Do the standard ECU's already use a knock sensor? I'd think any mapping that increased boost would need it as a safety margin. Actually, do you know if the standard ECU is adaptive? If I tip in optimax with a load of octane booster (or even Av-gas
Sorry for yet more questions!
Cheers!
First off I'm no actual scooby expert. I'm unsure if your engine/ecu will be fitted with any knock detection, as far as i know they dont. You can buy something on the lines like a Knocklink from Jap Innovations which will help you monitor it. Octane booster can only be a good thing in these engines aslong as its mixed correctly and consistently. Piggyback modules will help with the situation but could be costly and you wont get the features a stand alone system can give you. Look on ebay as you never know what shows up, i just missed buying a Possum Bourne ECU which was an adapted standard ECU similair to the scoobyecu for a mere £150!
The Possom Link isnt adpated. Its a complete aftermarket ecu. A little primitive for older cars, but it does work.
The standard ecu does use a knock sensor. As do Link, and Apexi PFC.
The std car should also be run on SUL fuel, not 95 octane.
Having a knock sensor doesnt make them adaptive. Its only there as a precaution against people using poor fuel etc. It is not 100% fullproof though,
The standard ecu does use a knock sensor. As do Link, and Apexi PFC.
The std car should also be run on SUL fuel, not 95 octane.
Having a knock sensor doesnt make them adaptive. Its only there as a precaution against people using poor fuel etc. It is not 100% fullproof though,
I guess the standard ECU is not adaptive then. Will still use optimax with octane boost to give some safety margin as it will be worked hard.
I think the knock sensor may be used as an over-boost limit too. My mate's Legacy road car has adjustable boost and if you set it too high it gets stuttery like a rev-limiter cutting in. I guess the over boost is starting to make it pink which is detected in the ECU which panics and cuts fuel/vents all the boost? Its pretty severe and we'd need to keep it well back from that! I guess the better octane boosted fuel will help
here as it would be able to withstand more boost before starting to pink? Well out of my depth here!
I think the knock sensor may be used as an over-boost limit too. My mate's Legacy road car has adjustable boost and if you set it too high it gets stuttery like a rev-limiter cutting in. I guess the over boost is starting to make it pink which is detected in the ECU which panics and cuts fuel/vents all the boost? Its pretty severe and we'd need to keep it well back from that! I guess the better octane boosted fuel will help
here as it would be able to withstand more boost before starting to pink? Well out of my depth here!
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