Discuss all things tuning in this section. News, products, problems and results.
Firstly current setup,
Ej255 close deck 14mm studs, 2.35l long rod destroker
big port 2l heads with chambers matched
Copper headgaskets, stainless orings in both head and block offset, 140ftlb on headstuds
IGN1A coils mounted 150mm from plugs, short 10mm leads, BKR7e plugs at .7mm gap
GTX3584, Equal length headers, 4in exhaust 45mm gate, id2600xds, MS3PRO ecu
Individ EGT, clt pressure ect all logged
We are making around the 500kw mark atm on 32psi, we have our own mainline dyno so it has spent quite a time on there.
Dyno no issues at all, tune as we normally would, and being a track car we have backed off at least 2-3degrees in timing from peak power
However at the track, we get half a days use before we start to see some fluctuating clt pressure readings, we also start to get some misfires only under high load at the same time
We removed the engine to find there was some leakage from the gaskets (checked bolt torque hadn't dropped on removal which it hasn't)
Reinstall with new gaskets, redyno and back off even further
Next track day same thing fine most of the day then same issue again
Do you think this is possibly a tune issue?
I'm tempted at this stage to revert to an MLS as we know that shouldn't have an issue at this level, but at later dates we do want to turn it up further
Could the misfires be a caused by coolant, or is it possible its the other way around and the misfires are causing the hg issue?
Any help appreciated
Is that the same with smaller spark plug gap- is it still misfiring? If you see spikes in pressure that means the engine becomes less efficient and that can ba caused by overheating it.
What compensations to do you have for rising manifold air temp and coolant temp. Are these temps higher than you see on the dyno? I would add additional fuel, and reduce timing as things that affect combustion temps rise. Are you seeing any overboost situations (really is the boost control working as expected)?
Reducing plug gap doesnt improve the misfire noticably
Temps are similar to dyno everything is well setup, only seeing circa 40deg intake temps and 90deg clt
Over 100 deg clt itll start to reduce the limiter, over 50 intake itll start to pull some timing but neither limits are being seen
Boost control is spot on no spikes at all. Overboost is set very agressively
Not an engine I'm too familiar with, but I understand there can be some cooling issues as circulation can be compromised at the rear of the block, and there is a known process for improving coolant flow there.
My thinking is that as it's a track car, rather than a sprint car, there may be some localised overheating - have you been able to match the coolant pressure spikes to what the vehicle is doing and where it is on the track?
You said you're mapping individual EGTs, did you notice any sort of deviation, or trend, starting before the mis-fire first became evident? I was thinking that perhaps there was a fuel vapourisation (boiling) problem - if so, it may show up as running fine under boost, as the fuel pressure will increase if boost referenced, but when off-boost under braking the pressure may drop to a point where the BP is exposed and vapour formed. That's very much a wild card, but some vehicles do have problems with heat soak of their fuel, especially if running E85 which usually has a lower boiling point.
What Dwell time do you use? Can you post the dwell table? Also, that plug gap seemed a bit high for this boost and application. Have you tried going about 0.55mm?