|Subject: Enging Tuner || New Question
|Sender's Name: Jules
Hello Alan, I have a major issue to resolve. I wanted more power for my stock 1995 V2 Impreza WRX Type RA sprint car, so commissioned a company to look at the car. The car only made 275 BHP on their dyno so they recommended an Alkatec ECU and remap to try for around 300 Bhp. I agreed and the work was completed. The car still only made 275 BHP but there was some improvement in torque and they suggested that the TMIC was the problem.
Two weeks later the engine broke a ring land on number 4 cylinder, and I was concerned about the map. They told me that it was likely to be my Turbo passing oil into the engine causing det or high compression. I rebuilt the turbo and fitted a new piston. The first company would not deal with me again as I had upset them by suggesting their Map may have caused the problem, so I took the car to another mapper. They tweaked the map, stating that the car had been mapped way too weak. I ran the car again and it broke ring lands on number 2 and 4 cyls within a few months, I built it up again and had it checked again. This time they increased fueling on no 4 cyl and made some other subtle safety tweeks. Then it broke a ring land on no 4 again. I was then told that the Subaru pistons are too weak and I needed forged pistons which would sort the problem once and for all.
So I had the engine professionally built with forged pistons and rods, uprated oil pump etc etc, at a cost of £3.5K. Ran the engine in exactly as instructed. Then fitted an uprated TMIC from a V3 car and this time it made 315 BHP on the rollers. I did one competition and lost compression on No 4. On stripping the engine I found all 4 pistons had scuffed and the rings were jammed in on 2 pistons, hence loss of compression.
I sent the pistons back to the engine builder for inspection, and he reported that there have been very high combustion temps causing the pistons to over expand and scuff the until the rings jammed in.
Thank you for your patience if you have got this far.
The current set up is:
now fitted FMIC, the car has 255 lph fuel pump with swirl pot, seperate regulator, 440cc injectors, 4 into one exhaust header, 100 Cell sports cat, apexi air filter with cold feed.
Here is my problem.
I have rebuilt the engine again with 4 new forged pistons, I will run in for 500 miles to bed rings.
Then I need to find out why this keeps happening. The car was reliable in competition right up until the Alkatec ecu was installed and mapped.
I think that there is an area on the map that is not mapped correctly but mappers maybe don\'t feel that the area will be visited, but with some of the driving that we do in Hill climb it is possible that the area is being sampled and the fuelling is too weak or ignition too advanced. I think that it happens on the down hill section in 3rd or 4th at very high revs. If you test the car on the straight by doing a 4th or 5th gear flat out full boost pull it all looks good with the in car wideband showing 11.1 - 11.3 AFR.
I am really worried about running it hard again as I have just run out of time with the car, the last build was done over 10 Months when I could find time. I think it has actually been out for a piston issue 5 Times now, more than I stated in my text, it\'s just hard to remember there have been so many occasions.
Is this something that you could diagnose rather than me just trying something and hoping for the best.I really need someone to look at the map and see what is wrong, or if there is something wrong with a component then I need to be able to diagnose this.
Sorry for the long mail, but I am desperate.
Hi Jules - Sad sorry tale! It's fair to say that the OE top mount doesn't give much leeway and fitting a front mount is a positive step. I'd say your original figure of 275 was about on the money for a stock RA to be honest. It's hard to pass comment on mapping issues without having sight of the data. Martyn will be happy to check it out for you. We set up a few hillclimb cars, including one who has a habit of taking class records! Just let me know when suits, and we'll book you in.