Help - Engine Problems...

[Shane001]

Hi guys,

I need some help to figure out what's wrong with the racecar.

Please though no guesses, I've already thrown a heap of guesses at this problem. Remember this is a track car only so I can't just take it for a drive to test every suggestion that has no direct experience or theoretical basis behind it. I'm hoping someone may have had a similar problem and therefore has some direct experience, or someone may have an idea of what could be the cause along with a logical explanation to back it up.

As well as the video following is a detailed diagnosis as well as a list of what I have already tried.

Firstly the video, you can clearly hear the difference in the note of the engine on subsequent laps;
http://www.youtube.com/watch?v=UAqfmzlw39k

Diagnosis;
So this problem first appeared at Bathurst earlier in the year. No sign of any problem on Friday or the first race on Saturday morning. Then all of a sudden as soon as I left the grid in race two on Saturday afternoon the car sounded as it does in the above video. Initially it didn't seem to affect power too much, but the further into the race I got the lower usable rev range I had. After a couple of laps I noticed there was virtually no power after say 7500rpm, next lap 7000rpm, next lap 6000rpm, etc until I basically had no power over 4000rpm which was then virtually undrivable on the race track and so I pulled back into the pits. Note these figures are examples only, not exact figures.

Initially we thought the problem was fuel, as we had used our fuel we brought with us all weekend up until race two, when we used fuel from the official (compulsory) fuel supplier for the event, so for the Sunday race we drained the tank and put our usual fuel back in (United Premium 100), hoping this would solve the problem.

Sunday race, same as the start of race two on Saturday, sounded like a tractor but no initial loss of power, but then power/revs dropped away over 3 or 4 laps so pulled back into the garage. Couldn't detect any problems idling or free revving, shut it down, checked the coil pack and other connections, found nothing obvious and went back out on track.

Initially after restarting the car it was back to as it was at the start of the race, didn't sound good but no loss of power, but again over 3 or 4 laps the useable rev range dropped away. Back in the pits, pulled the coil packs and inspected the front bank spark plugs, all looked fine. Fuel was burning clean. Went out again, same as before, didn't sound good but OK for a couple of laps before loosing power progressively lower in the rev range.

Following is what has been checked / replaced since Bathurst;
Checked rear bank spark plugs - all OK.
Tested coilpacks - OK but replaced with another set anyway.
Tested spark plug leads - OK but replaced with another set anyway.
Compression test - OK.
Leak down test - OK.
Tested injectors - OK but replaced the 275's with 210's as looking at injector cycles the 275's were too big.
Replaced fuel filter - cut open old one was OK.
checked air intake - no obstructions.
Fuel pressure - was not a problem.
And no engine diagnosis codes being thrown by the ecu.
Doesn't sound abnormal idling or free revving, only noticeable when actually on track, ie under load.

Engine all back together I went down to WP a few weeks ago to test. Initially everything was fine, the problem was gone, so whatever it was I assumed it was fixed. But then the second last session the problem suddenly returned. It was quite literally one lap it was fine, then coming onto the straight the next lap it immediately sounds sick (re video linked above).

So now back to square one. No idea what the problem is. Any ideas?

Edit: Another quick point to make, in the above video the engine sound changes coming onto the straight and coming out of turn 2 right around the point that Mivec kicks in, 5400rpm. I need to go back over my videos and logs from Bathurst, but at the time I did consider Mivec as related to the problem, but ruled it out due to the rest of the symptoms. But maybe it does have something to do with Mivec.

[aza013]

How is your oil pressure?
I only ask as you have not listed it.
It's like it's putting it self back into cold mode ( limiting power until up to running temp, slowly giving you more as it heats up ) but going in revers .
But I can't recall if you are running a full aftermarket ecu or not.
I would say that you have already checked this any way.

[spetz]

Fuel pump ok?

A friend once blew his cat and it lost all top end power as it became a restriction. Has the exhaust note changed?
Interestingly, the way it blew was by the battery short circuiting on the strut brace.

[aza013]

Fuel pressure - was not a problem. That takes out fuel pump.

[spetz]

Fuel pressure - was not a problem. That takes out fuel pump.

It may be cutting out while driving

[aza013]

If it was cutting out then there would be no power at all, as said the power is dropping but not going fully.

[Taz]

Are you running a cat converter shane?
I have a feeling it is something to do with the exhaust side of things, as you have no error codes - are you running a high flow aftermarket? is it old? etc

[Shane001]

Don't have an oil pressure guage, but I don't believe oil pressure is a problem, don't get a warning light.
Fuel pressure and therefore fuel pump is fine. I do have a fuel pressure guage, and pressure remains steady.
Don't run a cat. I run extractors out a side pipe with a Lukey muffler.

Also when it progressively looses power at lower points in the rev range, it's not like a fuel cut, so I don't think it's something the ECU is controlling deliberately.

I'm running the factory ecu with an eManage Ultimate piggy back.

[Shane001]

. Has the exhaust note changed?

Did you watch the video with no sound

[aza013]

Its almost got a egg beater sound to it lol.
But more of a lumpy sound.

[Shane001]

Another quick point to make, in the above video the engine sound changes coming onto the straight and coming out of turn 2 right around the point that Mivec kicks in, 5400rpm. I need to go back over my videos and logs from Bathurst, but at the time I did consider Mivec as related to the problem, but ruled it out due to the rest of the symptoms. But maybe it does have something to do with Mivec.

[aza013]

That is why I asked about oil pressure.

[Shane001]

Yeah I hear what you're saying, but there doesn't appear to be any oil pressure problems, nor does it appear to be directly a Mivec problem either.

ie. If it was lack of oil pressure, Mivec not working, then I would expect to see an immediate loss of power. There is no immediate loss of power, in fact the top speed for both the laps in the video above is identical.

Also, and I need to go back and review my videos and logs from Bathurst again to confirm, but from memory I ruled out Mivec, as the eventual loss of power progressed to an rpm point below the Mivec point of 5400rpm.

[payaya]

Sounds like the timings out. Have you checked under your valve covers? Dropped a valve?

[Shane001]

Finally got some time to review the vids and logs from Bathurst in detail.

It looks like the problem is somehow related to Mivec, as the 'tractor' noise kicks in as Mivec kicks in.

As per before initially there doesn't seem to be any noticeable loss of power, but the longer I drive it I do start to loose power over more and more of the rev range, and the sound is different again to the above video, it really does sound like it's missing, very much sounds 'sick'. Also at this point it sounds and lacks power both below and above the Mivec point, although the car is very rarely below Mivec while under W.O.T., less than a second at any point in time, other than the end of the Race 2 video where it's off Mivec for maybe 2 seconds up into Reid Park.

So, today I tested the Mivec oil valve switches, which appear to be working perfectly. Tomorrow I think I'll pull the rocker covers off and have a look.

Anyone got any ideas?

PS: For anyone who helps figures this out for me, there are hotlaps of SMP in December with your name on em

[aza013]

Valves maybe sticking open a little bit .

I'm at a loss, so just putting things out there.

[payaya]

F1 cars make a similar noise before they go bang!!

[Shane001]

F1 cars make a similar noise before they go bang!!

thanks for that papaya

[payaya]

Sorry the only way I can describe that noise!

[Shane001]

Pulled the front rocker cover off today.

First thing to notice was how clean it was, not a spot of oil sludge anywhere, completely spotless! Something to be said for modern quality synthetic oils. Everything was as clean as if it had just been dismantled, degreased/washed and reassembled!

Tested the switch again - all good. Secondary rockers and their pistons all moving freely. Camshaft to rocker clearances all OK. Nothing appeared damaged, broken or overly worn.

Will be pulling the rear bank rocker cover off tomorrow.