Mike Simard

2,000 ft/lbs of torque? I wonder what Mark Kibort feels about that?


What did you learn? Any ignition issues or mystery?

Congratulations on a good tuning session.

blown 87

Like the rest of us, left in the dust, looking for our doors.

ptuomov

This is the Dynapack dyno, so I think the torque value from this viewer software is the torque at the rear axle on fourth gear, maybe? The power is fortunately immune to the ratio, so the hp makes sense.

No ignition issues, other than that with too much timing it knocks like a **** and with too little timing it makes 100 hp less. I can get it to 650 Dynopack axle hp with 7 knocks per 10 second run on 93 pump gas. Above that, something would give.

On learning. Here's what I learned:

When you slam shut the throttle at 6700 rpm with 18 psi of boost, it's possible that the MAF sensor has a cow. Mine did. The voltage coming from the MAF is now all f'd up and the AFR on the way home was ten. So the car is a wreck for now, likely either MAF failure or LH failure. It's consistently rich as hell on both banks so I don't think it's a mechanical failure, those would show up more on one bank than the other. I drove it home, the MAF voltage is just all f'd up and all the associated problems.

I have a spare anything, except not a spare SuperMAF. I have a spare MAF, but that's regular not super...

In any case, I am out of commission for the 9/11 Shark party. I felt like a jackass showing up without a car at Carl's party, carrying just a dyno graph and a Victoria Secrets plastic bag full of booze. Only one person (who dropped my drunken *** off) saw the car.

ptuomov

Here's one who's been left in the dust: In the end of the day, I limped the car home with some problem that gave and AFR of about 10 in both banks. Any idea about what can cause a slightly hot-rodded car to have a malfunction that shows up as a wildly rich AFR in both cylinder banks? It's so rich it can't hold idle coming off high rpm or before it's warmed up. I nursed it home giving the standard Massachusetts consideration to red lights. So what's next? I'll check the lines, but wouldn't a leak make it lean, not rich? I am thinking it's either the MAF or LF.

hacker-pschorr

Dynapacks are cool, haven't really played with one since EFI 101. None in the area that I know of.

Is the MAF in the stock location?

Nice graph! Even with a small hick-up like the MAF wigging out, progress is progress.

ptuomov

Yes, within a very, very close tolerance.

dprantl

Maybe you munched up the O2 sensor? What does the ST2 show for O2 compensation?

Dan
'91 928GT S/C 475hp/460lb.ft

ptuomov

I am running it in a no-cat mode for now, so that's out of the equation.

Roy928tt

Nice, I like how you have modulated the boost so that you get a nice smooth power delivery, I'm also really impressed with the spread of boost, positive pressure at 2000 rpm, that also makes for a more driveable package.
I once drove a Nissan Skyline with 650 flywheel, but it doubled its' power between 5000 and 6000 rpm and was simply frightening, due to that.
I much prefer the power delivery of my own twin turbo 928.

I love your project, keep it up

Cheers Roy

AO

Super tuning session. 666 is spectacular. Do you know if that has a correction factor? The TQ is very fishy, and since HP is calculated from TQ, it begs the question if it's accurate. But it's clear you were there to tune, not throw a big number.

I don't see exactly how the MAF could richen the mixture. If anything, it would lean things out. Strange. Not sure how the superMAF works. If the super part of it broke, it would operate as a standard MAF - which would tell the LH there is more air than the tune - thus adding more fuel. Just a theory.

When you're nursing it home, were you making any boost? Just wondering about BOV?

Last thought would be fuel leaking in via vacuum lines from the regulator or dampners?

Mike Frye

666 is the number of the BEAST!

ptuomov

I am shooting for a flat torque curve, since that's gives me the most predictable drivability. Once I figure out how to extend the EZK map, I will then shift between boost profiles based on gear. This way, the rear wheel torque is as close to a constant as possible, which will also make the car as fast as possible under the traction constraint.

There was no correction factor, or more accurately, the correction factor was set to 1. The power is rear axle power, this was on one of those very repeatable and accurate Dynapack dynos that you bolt in place of the rear wheels. If I had been trying to get the highest possible number, I would have gone to the Dynojet in Malden and not worried about the knocks! ;-) So the 666 rwhp is legit peak number.

The torque number is I believe the rear axle torque on fourth gear. That explains the scale.

I don't know whether this dyno measures the hp directly and then computes the torque or the other way around. It doesn't make any difference anyway which way it's computed, as long as it's computed accurately.

The peak in boost at 3300 is by design. I set the gate pressure to a bit high level, which means that the car has to make above-target boost before the boost controller turns the control algorithm on. This is for tuning purposes, I wanted to make sure that the car was making boost at the set points for the mid range and top end even if we didn't load it long enough under 3500 rpm. With hindsight, that setting was probably not necessary.

If it were running lean, it could be a vacuum leak anywhere. If it were running rich only at the high rpm, it could be a boost leak after the MAF. But it's running rich everywhere, including idle. It's not smoking at all, but I can smell the fuel in the exhaust. So it's not oil making it to the combustion chamber. Furthermore, it is running equally rich on both banks, which makes it unlikely that it's a mechanical problem inside the engine.

I am left with three possibilities at this point: LH, MAF, or FPR. The FPR problem could be your idea of fuel leaking to the intake manifold from the fuel pressure regulator vacuum line. I don't think it can be just the FPR vacuum/pressure reference line, because that problem would make it run rich at idle and lean at full throttle and/or boost.

ptuomov

Yes. ;-)

This run had 680+ SAE axle horsepower, but 666 is a cooler number anyway!



Knocks are the only reason to run it rich and retarded. On higher octane gas, the stock long block would make all sorts of power when boosted.

FredR

Tuomo,

Those are amazing numbers- are you still determined to blow that poor motor to smithereens?

Well done.

Fred R

hacker-pschorr

Actually, you would go to a Mustang, SuperFlow, or DynoDynamics which have an infinite and user changeable base calculation system. First time at a Mustang dyno the operator was showing me how the drum weight is calculated and adjusted. To prove his point, he changed one field in his setup and suddenly a stock Miata was making 1,000rwhp.

AFAIK the DynaPacks are a locked system like Dynojets.