We are 10* at 6k, 18* out the top. EGT doesnt really start to go back up till we get back down to 15-16* at 30psi.

 

What has been failing on the oil pumps at those power levels(road race only I presume?), and what can be done to beef it up/prevent it?

 

Extended right hand corners at high G's uncover the oil pickup and can cause (not necessarily in this order or limited to one thing)-

Oil pump failure
Rod bearing damage or engine failure
Turbocharger failure in journal bearing turbos.

Solutions-

Run a 1/2 qt high
Then either get a Buschur modified pan or AMS pan
Ultimately a dry sump oiling system for EXTREME cars capable of High G cornering

 

Ok, I knew they were having starvation issues, wasn't sure if the pump was cavitating and causing the damage or if an actual gear was breaking due to the tq onset or something.

Thanks Aaron!

BTW, have the buschur pan's been working ok? I put an AMS pan on for a buddy and it's just a plain PITA to install and have seal properly and such, and is rather pricy, but if it's the only that works, ya gotta pay to play!

 

Aaron, got any thoughts on a scavenge pump setup to fill an external reservoir and then use the stock pump for pressure supply?

The possible benefit is that it keeps the high pressure oil-pump driven off the T-belt so the external oil pump belt would be less critical. You could monitor reservoir feed pressure and if you lost pressure there from tossing the scavenge pump belt, you would still have a small amount of time before you drained the reservoir and lost high side pressure.

Main benefit I'm thinking besides that is that you could use the stock front cover, filter housing, cooler, etc. You could probably even just modify the stock pan. Might actually be a lower budget solution to the high G issues?

Seems like the pump does fine when it has oil available? Feeding it from an external swirl tank would guarantee air-free oil to the stock pump and the scavenge pump might even get some vacuum benefits in the crank case.

Just thinking out loud...

 

Aaron,

Can you comment on a possible reason for the rate of the torque decrease from peak to redline? He loses 200ftlbs, and I experienced the same thing on my own build. Is this due to something with the efficiency of the motor or is it due to the turbo? There are plenty of dynos of non-stock frame turbos which have almost a completely flat torque plateau from spool up to redline.

-Acree

 

So far so good. I dont think he'd be able to keep selling them if they didnt work. The AMS can be a definite challenge to install. It comes down to if you need the extra 2 quarts for oil temp control or keeping the pickup covered.

Pondering...

Andrew-

Backpressure.

Luke's initial build was budget horsepower so #1 it doesnt have a very good recirc O2 housing on it, let alone a good O2 dump. Stock frame turbos, especially with larger motors, need to be able to breathe well. Gotta let you what you let in.

 

I'm currently running an open o2 dump and 3" exhaust and I still had the same slope.

-Acree

 

I've been thinking about doing this for a long time.
I have a baffled oil pan thread with lots of ideas.
A 2 stage scavenge pump would work great, with a modified oil pan (for the -10AN ports). A proper oil reservoir will need to be used so ensure all of the air is separated out of the oil.
This is the ultimate low cost solution for the Evo Oil surge problems. And it'll make horsepower from the vacuum pulled in the crankcase.

 

big turbos are capable of flatter torque curves. but that doesnt make more fun. they have a flat torque curve because they dont spool fast enough to make torque early in rpm band. 500 dropping to 350 is far more fun than a flat 400. early torque produces a more usable powerband. especially for a street, rally, or autocross car.

 

Bigger turbochargers make a flatter torque curve simply because the turbo isn't the restriction...

Drop the boost on a smaller turbo to where it's not the airflow limit and you still get a flat torque curve if the cam/head/manifold package is up to the task. HERE (solid line) is a stock turbo setup with a flat torque curve to 7500 RPM because it's on wastegate pressure and the turbo is capable of more airflow so it doesn't restrict the power and drop torque at high RPM. You can see the actual engine VE curve with torque peaking at 5500 RPM and holding solid to 6000 RPM, only dropping 10% torque by 7500. The dashed lines are 20 psi (dropping to like 16psi at redline) where the turbo is starting to show it's flow limits. Notice torque drops more dramatically after peak torque, losing 20% by 7500 RPM. Same setup, boost maxed out (23psi dropping to 17 psi vs. 25 psi dropping to 18 psi). Looks pretty dramatic on the torque drop, losing 30% torque by 7500 RPM.

Reason I make this statement is that if you up the boost high enough to make the turbo the limit, even a very large turbo can make a torque curve that peaks and falls. If you have a flat torque curve, it's simply because the boost isn't high enough.

I've tuned GT42R setups with the same torque curve shape as this green...it just happened from 6000 RPM to 9000 RPM, took 45 psi of boost, and peak torque was over 700 ft-lbs...

 

Remember that airflow == horsepower, not torque. With the turbo fully spooled and pumping out as much air as it can, your horsepower would (in theory, ignoring other factors) stay flat as the RPMs increased. HP is a function of torque and RPM, so to keep HP flat with increasing RPM, the torque must decrease.

If you did have a flat torque curve, then that would mean airflow is increasing with RPM. In other words, your turbo isn't as spooled as it could/should be at the lower RPMs.

 

Then come the other variables-

Boost control, MIVEC, Timing, etc.

Aaron

 

All great responses. Thank you all.

-Acree

 

500+ tq at 4k, now that's my kind of setup. I can't stand looking at graphs of the larger turbos where they are barely cracking 200 tq at 4k