Tuning my DR750s on Chrome

[Chris@Rvengeperformance]

Chris, you guys are talking over my head at the moment, but I thought one of your aims was to see how well the DR 750s kept up with the larger displacement.

Can you capsulize your thoughts on that?

yeah that would be nice to see. I think they are going to make huge torque and about the same HP, but at less boost and lower rpm. Probably will be running out of breath by 6500, vs the 16Gs which would probably pull great until 7500. If we are going to continue bench racing I expect to see 20 psi by 3000 easily, maybe lower. Todd so far saw about 50 more hp at 14 psi than I did, so I'd expect near 550 at 21-22 psi. Never going to run them hard enough to see 650 unless ray tunes it for me. Ray expected my old power band to shift down almost 800 rpm. Off boost should be awesome too.

I'm also stock heads and cams, so the 750s should be a little better match really. I'm sure it will respond down low exactly like 9bs or better. Since I am not octane limited I don't see much, if any gains running cams and heads with these turbos on this engine.

On the other hand you can't argue with the silly 750 torque ray has made on 16G/3.5/E85 setup. I can't see that much torque in the 750s on any setup. I just spend a lot of time driving this thing day to day in 1st/2nd gear situations and I know no matter what in those sorts of setups the 750s are going to respond better. Sure, a third gear pull may really close the gap, but that is not most of my driving.

Sorry, that is basically one big long thought and maybe is just repetitive.

Maybe this helps you too, I like turbo setups that you can drive around lazily and they still pull hard all the time. I like something that feels "always on" and you don't really have to be in the right gear all the time.

[J. Fast]

The big question you have to ask yourself is 40psi of oil pressure good enough to film bearings experiencing 500ft/lbs of tq at 2500rpms? That's diesel territory right there. 80psi of oil pressure at 500ft/lbs sounds a neck of a lot better to not deform the bearings. Gotta push the rev's out to get the oil pressure up to keep the crank floating. Just some food for thought.

[JasonY]

I definitely don't think that the 750s are too small for a 3.5L though. Yes the TD04 turbine is very tiny and restrictive. The 9 blade TD05HL turbine helps a great deal though and even with the extra 0.5L displacement I don't perceive the turbos choking off the motor. Todd made awesome power at 14 psi on the 3.5L. Matt firmly believes his stock intercoolers were a much bigger restriction on the 3.5L dyno than the 750s ever would be. The next question is whether or not you can safely get the car tuned. Supposedly Todd's 3.5L DR-750 car wiped out the main bearings from too early of torque while on Ray's dyno. Hopefully someone will clear it up but that's what was alluded to by Jason. I have no idea how simple or easy it will be to tune it out but it definitely sounds like you need to be careful. It definitely has me spooked to see that happening on a built motor with Ray tuning a flashed ecu which he should have adequate enough experience with by now having gone through multiple cars.

It had too much timing down low and got knock. Problem is the car makes over 400tq at 3k rpms and thats all she wrote for the mains. The ARC2's air signal to the ECU really caught Ray off guard and we didnt pull enough timing initially where we thought we needed to. The air signal is like half what the MAFT spits out to the ECU. So the engine load to tune for was way lower than anticipated. And when the car makes that much power that easily it doesnt take much to break something.

Jason

[Greg E]

The big question you have to ask yourself is 40psi of oil pressure good enough to film bearings experiencing 500ft/lbs of tq at 2500rpms? That's diesel territory right there. 80psi of oil pressure at 500ft/lbs sounds a neck of a lot better to not deform the bearings. Gotta push the rev's out to get the oil pressure up to keep the crank floating. Just some food for thought.

What car makes 500ft pounds at 2500 RPMs??

[J. Fast]

What car makes 500ft pounds at 2500 RPMs??

How much oil pressure does a turbo diesel produce at 2500rpm? How much oil pressure are you making at 3000,3500,4000? Think about it. Sounds like a very familiar situation.

[familyMAN]

Matt made 500 at 3350 on pump gas and meth at 21 psi with his stroker.

Warning: More bench racing....E85 and more boost could possibly get that down near or below 3k.

With 20w50 valvoline VR1, I had 25psi at 1k and 50 at 2k if I recall. Of course, higher above that.

[Chris@Rvengeperformance]

Even the old motor made ~50 psi at 2500 on 10w40. I can run 20w50 to get the best pressure possible. I wasn't there to see any logs or anything, but if you have the load at that rpm you could go from thinking it is going to run like 10-12 degrees of timing and actually run 20+

not great for anything. I can't quite wrap my head around how the fueling using the arc2 can work if the maf signal is that hosed, but I am sure there is an explanation.

[Chris@Rvengeperformance]

Well, hey the good news is I located a pristine crankshaft from a debonaire and it is already on the way to ray's.

Ironically it actually was one of the cranks trevor pulled from one of this blocks when he installed the 75 crank.





Minor crank imperfections are not that bad for the stroker crank, but if they had a spun bearing in their live they may make them unsuitable.

[Greg E]

How much oil pressure does a turbo diesel produce at 2500rpm? How much oil pressure are you making at 3000,3500,4000? Think about it. Sounds like a very familiar situation.

I don't own a turbo diesel so I couldn't tell you. Couldn't tell you the oil pressure numbers these motors were seeing either.

What the evidence suggests is both these motors with DR750s were killed from crank flex caused by too much compression in the mid range RPMs. The evidence which supports this is the center mains being worn heavier than the outer ones which is a sign of crank flex.

The faces of the bearings were flattened smooth not burnt from lack of oil pressure. To be fair, I personally haven't witness this but this is the information that was reported to me.

[J. Fast]

Matt made 500 at 3350 on pump gas and meth at 21 psi with his stroker.

Warning: More bench racing....E85 and more boost could possibly get that down near or below 3k.

With 20w50 valvoline VR1, I had 25psi at 1k and 50 at 2k if I recall. Of course, higher above that.

Towing my car to the track with a 7.3 F350 I see 60psi at 2200rpm with 1200F EGT.

At 2200rpm in my GT on Platinum Ultra I see about 40psi.