RS America live remap at the dyno

[Steve W]

Performed a live remap of a black 93 RS America at the dyno today. The engine is a fresh rebuild with RS cams, B&B headers/muffler, drilled airbox cover, and a lightweight flywheel. Engine needed a full rebuild as everything inside had been burned up. Runs were done with a stock chip - blue curves below, a full remap for 100 octane race fuel - red curves, and a remap for 91 octane street gas - green curves. All runs were done this afternoon on a Dynojet 248. What is shocking is that with the stock chip, the air fuel ratio above 4500 rpm goes very lean, and almost to 16:1 above 6000 rpm. Not only would that burn up the motor by breaking the rings and melting the pistons in no time, but the knock sensors must have been going hyperactive causing a dramatic loss in power, especially after 5500 rpm. You can see the difference in power at 6300 rpm where the stock chip is making about 173 at the wheels, while the remapped programs are making 246 and 259 hp, a gain of 73 hp and 86 hp at the wheels respectively (or 100 hp at the engine). What's just as shocking is that the owner ran a full race at Thunderhill in Northern California last weekend before driving the car down to Los Angeles - and the engine still survived.

The car also had a bad stalling problem with a lightweight flywheel, and that had been fixed. It returns to idle perfectly, with and without the AC on, you can't even tell it from stock.

[Don Plumley]

Wow - wish I could have you chip my 96!

[ninesixfour]

246 at the wheels on 91 octane?

[tshih]

Is the engine's distributor running with a broken belt when the engine burned up? Has anyone come up with a sequential FI system like the Motec with individual coils to do away with the twin distributor problem?

[Steve W]

Thanks guys.

I guess I should have been more clear. The motor didn't burn up as if it was on fire, but internally it suffered a lot of wear from running too hot from being lean. I didn't get into the details with the owner, but he mentioned the shop was surprised to see it coming in for a rebuild so soon, and at the the amount of damage he saw inside. Valve guides very worn, valves looking burned ect. It wasn't until we threw it on the dyno did the cause become clear. The stock twin plug system works well as long as everything is properly functioning. There are a lot of guys out there I find that have one side or the other improperly functioning or not firing at all, but don't know because the other side is still firing the spark.

[ischmitz]

Steve,

nice work, man. However, I am baffled why the engine would go so extremely lean on the stock chip at higher RPM's. Are you saying the RS cams and the drilled air box take it so far away from a bone-stock 964 engine

What exactly did you remap? The WOT map or the full 2D part throttle map. I take it the dyno runs are WOT runs in 3rd or 4th gear, right?

Cheers,
Ingo (from Japan)

[Steve W]

Hey Ingo,

I couldn't really tell you - the cams and headers probably contributed, drilled airboxes don't really change things much. Dynoing without an airbox and filter makes only a 4 hp difference starting from 4800 rpm up and barely affect the AFRs. About 2/3s of 911s come in somewhere you'd expect, the other third come in way off the wall. The region after 5000 rpm is usually where the greatest variations come in as the barn door of the AFM has already maxed out, so the DME can only depend on the preprogrammed fuel maps to determine injector timing. Untouched or never removed engines are usually the most consistent. I dyno mapped 4 POC race cars of basically idential configuration in the past 2 months, (stock internals, headers and open pipes) and they mapped out all over the place. No one was even similar to the other - the fuel maps varied by 15% from one car to the next, which would result in as much as a full 2.0 AFR point difference rich or lean if the program from one car was plugged into the other.

I remapped WOT, and reworked the PT map too. You can hold a load at a specific rpm on the engine as they have rpm modulated internal brakes.

[mjshira]

steve this is probably the exact mapping I need for my RS clone..

[Steve W]

Hey James, as much as I'd like to see this mapping match your car, I seriously doubt it would even come close. Better off to provide a dyno AFR plot and map it to that, or bring your car to L.A. and we'll stick it on the dyno.

Ever figure out your LWF stalling problems? I just developed a new solution that's beyond all the old tricks.

[mjshira]

no, I am still having the stalling problems. I'll drop you and email. I've tried and older chip of yours and it helped but it is still happening. I've got 2 964's at the moment. The one I am working to get perfect is the one I am selling. It won't stall if you put her in neutral before you come to a stop... strange huh?

the custom chip will be for my other 964. I'll get a dyno run and data log for ya some place local. I wish I could 'bring it to LA' but that would be a LONG drive having done it twice.

[ischmitz]

Originally Posted by Steve W

Hey Ingo,

I couldn't really tell you - the cams and headers probably contributed, drilled airboxes don't really change things much. Dynoing without an airbox and filter makes only a 4 hp difference starting from 4800 rpm up and barely affect the AFRs. About 2/3s of 911s come in somewhere you'd expect, the other third come in way off the wall. The region after 5000 rpm is usually where the greatest variations come in as the barn door of the AFM has already maxed out, so the DME can only depend on the preprogrammed fuel maps to determine injector timing. Untouched or never removed engines are usually the most consistent. I dyno mapped 4 POC race cars of basically idential configuration in the past 2 months, (stock internals, headers and open pipes) and they mapped out all over the place. No one was even similar to the other - the fuel maps varied by 15% from one car to the next, which would result in as much as a full 2.0 AFR point difference rich or lean if the program from one car was plugged into the other.

I remapped WOT, and reworked the PT map too. You can hold a load at a specific rpm on the engine as they have rpm modulated internal brakes.

Steve, after thinking a little bit more about what you wrote I have a couple of comments. Please don't take this the wrong way. You do excellent work and by no means do I want to rain on it - I merely want to put out some thoughts and wonder what you think about it. I am not affiliated with a certain individual in the LA area who engineers systems or was it the other way around, errr....

So here it goes: As far as I understand the reason for these lean AF ratios are either too much air (unlikely) or not enough fuel. I don't think that different cars vary so much in their efficiency to pull air into the engine. So I would lean towards there not being enough fuel. Two reasons come to mind as to why there is not enogh fuel:

- fuel pressure
The 964 engine has a vacuum-actuated fuel pressure regulator that raises fuel pressure as the engine load goes up. If that mechanism is not working the amount of fuel would be reduced.

Also, if for some reason the base fuel pressure if too low the car would run lean across the board. While under part throttle the DME can correct for this due to the closed-loop operation it is not able to do so at WOT.

- injector performance
If one or all injectors are not performing optimal (poor spray pattern, wrong amount of fuel per pulse duration, gunked up) the amount of fuel would again be reduced causing a lean condition. Again, while the DME can correct within certain boundries during part throttle it can't do that in open loop at WOT.

So I am wondering if remapping a 964 could be masking an issue with its fuel delivery system. Have you checked into that?

Next, when you say the barn door maxes out at the upper end of the RPM spectrum I can see where this would cause part throttle issues. But again, under WOT the DME does not take load into acount. The only input is engine speed. So the maxed out barn door by itself would not cause a lean conditions seen in the stock dyno chart.

The reason I am trying to poke holes into your explanations is that you got me seriously worried about my 964 now. I think when I get home I have to fire up my trusty LM-1 and do some runs up the hill (poor mans dyno ) to check how my AFs look. I don't want to rebuild that puppy again due to detonation.

Cheers,
Ingo (from the land of the rising sun)

[Steve W]

Ingo, all very excellent and valid points you have brought up - it would have been great if you were there to poke around. Unfortunately, when the dyno clock is ticking, and the owner need to get back home to San Francisco later that evening, I’m not in the position to be a mechanic nor have the resources to trace a condition that could take hours to days to locate and fix and may not even exist. All you can do is inform the owner to make sure everything is mechanically correct with his car prior to the dyno, so as not to end up with remap that band aids for a mechanical defect. If an aberration is caused by something simple, I try my best to fix it, but beyond that all you can do is provide your best opinion and suggestions. In this case I recommended the owner have the fuel pressure checked, and if his mechanic found anything, a remap would probably be necessary.

However it’s not immediately apparent from the data that the fuel pressures are off. If the pressures where higher or lower by a few psi, it would show as a shift in the AFRs throughout the entire RPM range. The air fuel ratios in the chart above plot out and remap to exactly 1-2% to where a car of this configuration would read from 1000 up to 4500 rpm, which is counter to the low fuel pressure or clogged injector theory. Another theory could be that the injectors are approaching 100% duty cycle, so control is being lost, which I’ve seen before although I don’t have enough data to make such a conclusion in this case. Some of the guys who run bigger bore 964 racing motors are also using bigger injectors and/or higher system pressures to prevent that from happening.

Actually it’s a misconception that DME ignores the AFM at WOT. At WOT, the output voltage from the AFM is still used to compute the full throttle injector output, which is a good thing as it means the DME is still compensating for flow changes, at least up until the barn door maxes out somewhere around 4500 rpm. Theoretically it is possible that the V out at the AFM’s max is below spec, but that would not be the first thing I would check unless there were wiring or corrosion problems. But I have found lots of wear and contamination inside the potentiometer section of a 964 AFM each time I checked. Usually the resistance tracks show wear and pitting in the idle and low rpm range. Because of the upside down mounting arrangement of the AFM, we once found 3 tablespoons of old motor oil inside Tyson’s!

Regardless of what you see from this car, I don’t think you have anything to worry about with yours. I’m sure you’ve run tests with your LM-1 before and as long as everything checks out within the norm, you’re fine.

[scooter911]

can this chip be duplicated and move from 964 to 964 with the same or at least similar results?

[mjshira]

Yes

[scooter911]

So why aren't we all on this kool aid?

[mjshira]

I am not going to get into a back and forth with you. But Steve's products are the real deal. If you don't wish to buy them, that is your call. That said, the guy that built my car runs one (and did this dyno run) and more than that having them (Steve's chips) in my cars has proven make my cars run better and faster.

so if you wish to flame Steve, Tyson and me and call my statments 'kool aid' that is up to you.

[scooter911]

Hey the kool aid is simply what many people drink when they found the product that works great for them and they believe in it! I just wanted to know if there is kool aid for everyone and if their is, will it taste as good in my car as yours or anyone else's!

[ischmitz]

Scooter,

to answer your questions: Yes, pretty much any Motronic-controlled engine will benefit from a chip tuning. You can buy "off the shelf" versions and there are plenty of products on the market. Some with outragious claims and others that really work. There are several different applications (tune for race gas, increase rev limit, tune for pump gas, etc.) You need to know exactly what you want to get get.

Steve Wong goes one step further: He fine-tunes the chip using the very engine it is supposed to work on. While this is much more work and requires dyno time ($$$) it has the additional benefit of fitting the engine like a glove. And from all the testimonies he does outstanding work. Do a search for chip & Steve on the board.

I guess your initial post sounded like you were intending to simply copy this work. I hope this wasn't your intention, right.

Cheers,
Ingo

[scooter911]

I have trouble duplicating work I have all ready done let alone someone else's. I am just looking for more power and thought that if this chip works on one person's car and they are happy(see Dyno results) then could I use the same chip bought from the same person and just simply plug & play? If I can then I would like to know who to contact to get some of this...kool aid Would I still require dyno time?
That is and was all I am looking for.
Thanks

[Steve W]

Duplicating the chip is not the problem - matching your car would probably be. Porsche motors, in particular 964s, can be sensitive to engine modifications, and when engines have such gross abberations, the custom remaps usually only work in that particular car and would not match another. Fine tuning a Porsche engine is not much different than fine tuning a musical instrument. For a simple a plug and play chip, I'd select from one of off the shelf chips from a reputable tuner, such as the NBD switchable chips from Pelican. However for the best, a custom remap fine tuned to your motor and dyno data is the only way to go and second only to a live remap.

The more you see, the more you realize how inconsistent everything is. Here's the dyno result of a 964 Cup Car with the factory Cup brain and chip and Cup exhaust. Here you can see the engine going lean from 4900-5600 rpm, and the resultant power loss - with no resemblance between this dyno and the one posted at the top of this thread, the lean spots are in completely different regions.