I’m Sander from the Netherlands. I drive an MGF for my own fun and we drive a Lotus Exige (normally aspirated) in the BTCS. I’m not driving it myself, during a race that is, but I’m one of the guys responsible for getting it through a race technically
Last week we’ve had the 12hrs race in Spa Francorchamps. We have the Lotus supplied Janspeed exhaust because our Exige has the Exige Cup kit fitted. (Including ITG airbox/EFi ECU/torsen LSD/roll cage/70ltr tank/…/…)
Afer 4 hours we blew a big hole in the exhaust manifold which also had cracked fully round on the weld of the y-conector with which it goes from 2 to 1. (behind the backbox) We’ve welded some (stainless) steel plates over the hole and started racing again. After about 3 hours it cracked again but not in the same place, there was a big hole where once the second lambda (behind the cat) was. So this time is was the cat-backbox assembly instead of the manifold. We’ve welded it again and finished the race.
My question to you all is if there’s a better manufactured exhaust system which will withstand the torture of a 12hrs race easilly. Could it be the (stainless steel) exhaust has cracked because our Exige is running lean/rich ? Or is this normal behaviour and would mild steed be better for this application ?
Sander, it sounds like a fairly classical fatigue failure brought about by extreme levels of vibration/force and possibly a reduction in material strength brought about by running with excessive exhaust gas temps.
If you could send me a few photos to robert.corbishley"at"gb.mahle.com I’ll have a look and consult the structural analysis guys for you and see if the fabricators can recommend any improvements.
Is it the complete Janspeed exhaust manifold, cat and silencer? I’ve heard from PTP about leakage problems with these manifolds which has forced them to take them off the market at the moment.
Regarding the engine management, which ECU are you using and who mapped it. What AFR do you run at peak power and are you measureing the exhaust gas temperature? My old caterham ran AFR of 13.8:1 at the top end which is great for power but does get bloody hot. On the Caterham it wasn’t such a problem due to the high airflow through the engine bay and the short bursts of top end that I would achieve on the road but on a racing Lotus it would cause problems. Stick a K type thermocouple in the primary pipes as near to the head as possible and log the temps. Anything over 950�C is cause for concern.
A few years back MG tried to lean out the MGF at peak power to reduce fuel consumption and the cars started to crack manifolds (alledgedly).
Also (even though I own an S2 myself) I’m not familiar with the arrangement of the hangers, i’ve you have a diagram/photo of the whole exhaust it would be useful.
Are you free to fit whatever exhaust you want? Presumably with a motorsport cat? We could develop a specifically tuned manifold to suit your car and re-map it on the dyno. I’d love to build a simulation model of the Toyota engine and see exactly how much you could get out of it.
Drop me an email or call me on 0870 157 3193(work phone).
The car looks absolutely beautiful, don�t suppose there is anywhere (a website or something) where we can see some more pictures , I had a look at racingworld.be but I couldn�t find many of your car .
Is it the complete Janspeed exhaust manifold, cat and silencer? I’ve heard from PTP about leakage problems with these manifolds which has forced them to take them off the market at the moment.
Is this official? The PTP website still refers to “The silencer alone adds 12bhp of peak Power, and when used in conjunction with Janspeed’s 4-2-1 manifold and sports catalyst gains of 10bhp and 18lbft of torque can be felt from as little as 3000rpm.”
What do the “experts” - with over 40years experience - at Janspeed say?
I don’t know, we’ve got the exhaust through the Belgian Lotus dealer. We’ve confronted him with the problem but I haven’t heared anything yet.
If you could send me a few photos to robert.corbishley"at"gb.mahle.com I’ll have a look and consult the structural analysis guys for you and see if the fabricators can recommend any improvements.
I’m sorry but in the “heat of the moment” we didn’t take pictures. The holes are welded over again with stainless steel plates.
Is it the complete Janspeed exhaust manifold, cat and silencer? I’ve heard from PTP about leakage problems with these manifolds which has forced them to take them off the market at the moment.
Regarding the engine management, which ECU are you using and who mapped it.
It’s the complete system. We are using the EFi ECU. It came with the “Cup-kit” It isn’t mapped on the car but came with a default mapping.
A few years back MG tried to lean out the MGF at peak power to reduce fuel consumption and the cars started to crack manifolds (alledgedly).
Also (even though I own an S2 myself) I’m not familiar with the arrangement of the hangers, i’ve you have a diagram/photo of the whole exhaust it would be useful.
Are you free to fit whatever exhaust you want? Presumably with a motorsport cat? We could develop a specifically tuned manifold to suit your car and re-map it on the dyno. I’d love to build a simulation model of the Toyota engine and see exactly how much you could get out of it.
I think it would be best for us to check the AFR on a Dynobench. I can’t find any good diagrams I’ll try to make some pictures of the car next time I’m working on it.
We are racing in the BTCS so I think any exhaust will do. I even think the cat could be scrapped aswell but I’d have to look into that.
Thanks for the offer of develloping a custom manifold. I am in the Netherlands however so it would be quite difficult getting the car with you.
The car looks absolutely beautiful, don�t suppose there is anywhere (a website or something) where we can see some more pictures , I had a look at racingworld.be but I couldn�t find many of your car .
Hi Sander, it sounds like the exhaust has given a significant increase in airflow and the fuelling needs to be modified to keep up. If you have access to the ECU then this shouldn’t be too hard to sort on dyno.
I spoke to an Exige S owner who’d fitted a modified cat, exhaust and airbox and his car is now running lean also. I’m not sure how he is planning to fix it. Possibly fit an adjustable fuel pressure regulator?
On the materials side, you were correct, mild steel is much better for exhausts. Stainless steel “work hardens” so they do become brittle and crack with time. The best material is Inconel but that might get a bit expensive!!
Looking at your photos a grey Exige is shown with and without the supercharger. Is this the same car? Do you fit the cup kit yourself? I want one!!
I think the next logical step would be checking the AFR. I think fitting an FPR to a mildly modyfied K-series on a stock ECU will do the trick but I don’t think this will be the ideal solution for the Toyota running an EFi.
However it might prove to be quite difficult getting the car mapped correctly somewhere over here.
The one with the supercharger isn’t our Exige. We’ve fitted a few of the N.A. cup parts ourselves. (Exhaust, ECU, Filter, big fuel tank. The rollcage, fire extinguisher etc. had to be fitted by certified personel.
Is it the complete Janspeed exhaust manifold, cat and silencer? I’ve heard from PTP about leakage problems with these manifolds which has forced them to take them off the market at the moment.
Is this official? The PTP website still refers to “The silencer alone adds 12bhp of peak Power, and when used in conjunction with Janspeed’s 4-2-1 manifold and sports catalyst gains of 10bhp and 18lbft of torque can be felt from as little as 3000rpm.”
Rob
I’m assured that these problems have since been resolved
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