Revisions on the Racecar - Suggestions?

[Robert Venable]

WTF is happening? Do you guys think that the oil is airerating (coonass spelling for you)?? Is the pres. relieve valve opening due to the quick surge of oil volume and not recovering as it drops??

Your pick up tube screen is partialy clogged and the volume of oil cannot keep up with demand. I have also seen cracks in the pick up tube that suck air when pressed.
If you take the time to run the oil pump without the engine running and watch the oil level in your oil pan, you would be amazed, it scared me to death the first time I witnessed how it works, the amount of oil in the oil pan drops to about 1 1/2 quart, the rest is up in the engine[/quote]

That kinda make since, except for how clean the inside of this engine is.

When I removed the valve cover at about 205K the engine was cleaner than just about every single engine I've taken apart in the past. My grandfather changed the oil religiously at 3k, and used Diesel oil (High Detergerant). Also, every oil change since I've gotten it. I've flushed it with a 50/50 mix of ATF and Engine oil (drain the oil and filter, reinstall filter, add 2 qts 5/30 or 15/60, and top off with ATF. Run engine for 30+ min., mostly idling with the occasional rev to 4k).

Either way, I guess I will see if you are right this summer.

[jeffball610]

Some of the items here peaked my interest and have some input on them.

The DSM motor runs at 11psi at operating temperature at 750RPM. On a cold start, it's not uncommon to see nearly 100psi measured at the oil filter housing before the oil filter. There is a mod to help that relief spring and I'll post it when I find the link. I know for a fact that John Shepherd runs 85psi and this is done at almost 10k RPMs. I don't know his secret, but somehow it works.

Removing the balance shafts and blocking off the oil holes improves oil pressure. I saw a 4psi climb at idle on my 92 TSi when I did this. Removing the oil squirters does the same, though I don't know to what extent. Most DSM racers are drag guys and running the engine hard for 10 seconds you won't miss those squirters. It is true that aftermarket pistons have different heating properties. (or whatever) Alot of forged aluminum pistons will cool much better than stock and may not require squirters. I for one will keep mine for safety's sake.

The distortion under heat is very real. Alot of guys running early JE pistons complained of "piston slap" on cold starts. This is because the pistons themselves where not up to operating temperature. Also, the distortion from head toque is also very real especially in DSMs. It is suggested that you torque the head to spec before you torque the main caps due to it's distortion. How weird is that?

And as far as blow off valves go, it's still debatable. It does proven to help eliminate a reverse surge on your compressor. In limited driving and race applications, it may not be neccessary. For guys running stock DSM MAF setups (even 2G conversions) the recirculation of the BOV is known to cause problems when eliminated. Mostly it causes rich conditions under closed throttle shifts and poor idle. This isn't really related to the other issues, but shows what issues can happen no matter how small.

That's about all the info I have. I don't really see why the motor would have run lean other than Bill's thought on high RPM vacuum off throttle. It makes sense, but I don't know that it would cause this. I would imagine a fuel cut under those conditions and therefore no combustion would take place without the fuel. But I'm not as smart as some of you, so I'll stop there.

[DJpowerHaus]

I'll catch up on all the recent posts in a bit. I wanted to post my injector test rig:




Justine is holding my other bottles hostage.

[Bill Hincher]

I don't know Jeff, but the gaskets look actually sucked in not blown out. If the balance of boost is left out of the plenum, as Old Colt says, on deacceleration ,why would the damage be behind the plate? Is the Turbo capable of generating that much suction when spooled up, that it could pull a vacuum in the plenum so hard it sucked in the gasket?


GREAT JOB on the injector set up, we used to use glass baby bottles because they had graduated markings on the bottle and it was easy to see the balance of flow that way

[Bill Hincher]

this would also explain lean condition burning out the pistons