John Speake

Tuomo and John are quite capable of eliminating the knocks they had during their last experiment. They have the tools to do so, but didn't think it was important to retune for those runs.

Thom

Considering all the work that's been carried out on this project I'm surprised that the old Bosch ECU was not upgraded to a more modern speed density unit using closed-loop knock control/boost control and all the flexibility of a modern interface.
Was the engine harness rebuilt?

ptuomov

The ECU hardware is all stock. No, the harness was not rebuilt -- it's barely broken in at a young age of 26 years. ;-) There's a standalone boost controller, eboost2, that is really good value for money.

Part of the challenge we have is to try to push the stock parts as far as we can. Projects are only fun if there are some constraints, otherwise the solution ends up being buying a modern, new car in pieces. It's the curse of no financial constraints that you have to come up with some other constraints.

It is however an interesting question where the stock ECUs fall short of the maximum potential. I think there are a couple of areas:
(1) more resolution at higher rpms. (This is being remedied by JDS.)
(2) the ignition and fuel grids to coincide. This is simply to make tuning faster.
(3) more columns and rows for the fuel and ignition maps
(4) individual cylinder fuel and ignition trim maps
(5) boost control integrated with ignition control and knock sensors
(6) traction control integrated to the ignition control and boost control
(7) throttle position switch input instead of a continuous throttle position sensor input

It appears that I am in a minority, but I like the hot-wire mass air flow load measurement. It's very flexible and self correcting. There's some flow restriction, but I think that's really minor. I wouldn't go to speed-density as long as using the stock intake manifold. With a "sheet-metal" intake, it probably would make sense to go to speed-density. By the way, JDS are working on a speed-density conversion kit for the stock ECU's.

Speaking of sheet metal intakes, I am not yet convinced that the stock intake is the most binding bottleneck in a boosted car. So far, we seem to be doing fine with it. At some point it will become the bottleneck but I am interested how far it can be pushed.

Another system that I don't think is going to be a bottleneck soon is the ignition. This is because we're running 93-octane pump gas. With alternative fuels, the ignition would probably have to changed, but for pump gas the stock ignition appears sufficient.

ptuomov

There's no secrets in what we're doing now. It's just all garden variety debugging of a system as the manifold pressure is increased. Fixing things as they come up, and running experiments to find problems and solutions. The immediate goal is to figure out how to get the motor produce a stable boost level higher than 18 psi. The current problem is not making the engine survive a high boost, it's simply to get it to produce a high boost. The survival is not an issue when doing quick sweeps on a Dynojet. It's somewhere between unglamorous and boring for others to watch or read about this kind of work, I was just updating the thread to explain what's happening.

Perhaps you are making your point in a too subtle way above... ;-)

I think you are essentially correct in that you have to let the engine knock somewhat when mapping it because otherwise there is no way to learn where the knock threshold is. The question is how efficient your learning method is. How quickly can you learn the knock limit (or the knock probability function) with the fewest possible actual knocks.

One piece of equipment on my wish list is this: http://www.tfxengine.com/ It is expensive starting at $7k and if I buy it I don't want it to collect dust in a box, so I'll only pull the trigger once I know I can get it installed immediately when delivered. This equipment allows measuring irregular combustion the same way that car factories measure it, with a pressure sensor in the combustion chamber. I don't think that this equipment changes fact that you have to go to the irregular combustion region in order to learn where that region is, it'll just make it easier to learn a lot quickly once there.

ptuomov

We're planning to share all the interesting data. There's no secrets here. It's just that the necessary experiments run to debug a system to produce a high and stable boost are boring and produce boring data. Once we get interesting data, I'll share freely.

Thom

I find it odd making a point in keeping the stock ECU when so manys changes have been done to the engine, and that was not "only" modifying external parts such as exhaust/turbos but also replacing inner parts such as pistons to lower the compression ratio.
I understand that moving to an aftermarket ECU and building the engine harness may represent a major investment (not just in money but also in personal free time) for the average DIYer, but using a speed density-based ECU should make turbo/intake/exhaust swaps a doddle compared with a MAF system - BTDT.
Of course we can still use a MAP signal to ponderate fuel/ignition tables in the stock ECU but that is not the right way to do it, IMO.

Anyway, thanks for the open discussion. I totally relate to the "if it's too easy it's not worth doing" stance, and am looking forward to hearing of your progress.

ptuomov

This explains some of the confusion. Currently the engine in the car is completely stock with no internal modifications whatsoever. No porting, cams, stock 9.4:1 compression. The only thing that was done is that the intake and valve covers were powder coated. So we are keeping as much of the engine stock as possible, and seeing how far that gets us.

I personally find it remarkable that John can get 700hp out of the completely stock engine with reprogrammed ECUs and that the whole setup currently on the car can be replicated for about $20k.

I agree that if one is fabricating a custom intake, then speed-density is the way to go as the MAF placement creates packaging constraints.

When more internal engine modifications are made and as the engine starts resembling the stock engine less and less, we'll also reevaluate the question of what engine management system to use.

BC

It rarely does for even the best of us.

What program are you using to run the simulations. Some have been found to be WAY off and others within 200rpm of correct HP levels shown on a real world Dyno
If you are allowing knock to happen at your power level - what are you learning, and indeed what questions are being asked? other than how to set a fuse on a bomb?

Why reinvent the wheel? Has the manufacturer been spoken to about your system? Not John. The turbo makers. The Wastegate manufacturer. They know a WHOLE HELL alot more than you, me, or John. You have specific volumetric information, barometric info, and turbo size and compressor charts. You should be able to hit a target. Otherwise it sounds like you are guessing.


This statement is incorrect and I don't know why you would suggest it. No one is suggesting race gas, especially not me.

But its still knocking. Why do you think that is?


Is this because you need to know more about the wastegate and its operation? Have you spoken to the manufacturer?

BC

This is part of what I am trying to say. Going in this direction with the tools available to RUN the engine is a false premise.

BC

Its statements like this where I only see you blowing this engine up and stating to the masses that you have found the limit, when you found nothing but purposely-constrained tuning tools and detonation where it existed before and always will.

Stock ignition systems don't always work with alternative fuels and sprays BECAUSE the Mixture is MORE difficult to ignite ON PURPOSE. Its knock resistance goes up, as does its resistance to actually lighting it off properly. So what essentially you are saying, emphatically above, is that you are using an inferior ignition system because you know the fuel is inferior and is capable of disastrous levels of detonation within the load and air flow ranges you are tuning in.

ptuomov

The current issue we're having is not really an internal combustion issue, it's a general turbocompressor issue. We're trying the get the boost up in the high rpms. Since we're producing exhaust and the turbocharger is spinning, inability to ramp up the boost at high rpms is most likely not an issue with the engine itself.

For debugging purposes, the car was run with a constant boost profile today. It's simpler than the rpm specific profiles, and eliminates one potential issue. The knock retard was on since this what not a mapping session.

For those of you who are curious, this is what the power and torque curves look like when the car is run on a constant boost profile:



The peak power is in the same ball park as the graph I posted earlier, but now we don't have that flat torque curve. Instead, we have a flat power curve, making over 600 rwhp in the 4300-6000 rpm range.

More generally, we're hitting some sort of bottleneck at about 700 rwhp. The main hypotheses right now are boost leak that shows up at 18 psi (for example something flexing), low pressure cold side restriction, or some control issue.

Hitting bottlenecks by the way is not unexpected. John designed his kit to be correctly sized, with margins of safety, for about 600 rwhp, and we're significantly over that. In a well engineered kit, everything runs out of capacity at about the same point because it's correctly sized for the application, with a margin of safety. Now we just have to identify the bottlenecks one by one and keep solving them.

This is a science project. If you just want drive a fast car, I can say that for someone looking 600 rwhp the existing twin turbo kit is a completely problem free system.

Roy928tt

Go You Good Guys !

Keep it up Tuomo and John, There be Dragons out there, but I have no doubt you two will succeed in pushing to a limit.

Why on earth anyone would need over the 600 hp the kit was designed to deliver, is beyond me, but wanting it is no crime.

Bring it on.

Cheers Guys

Tampa 928s

I think the bigger picture is how much can you get out of a stock set-up. If the goal was to get the the highest H.P. 928 out on the road it would be done by now. (what about our Nos enriched British friend was he not over 1000 H.P.
I am seeing a lot of resources, money and time fuled by the passion to see how close to the edge you can take it and still turn the key and drive it every day.
This project is in very capable hands the upside is all the R&D is being funded at no cost to us and will only filter down to the 928 community.
This thread seems to be like paper in the scientific journal a hypothesis is presented skeptics bring up that your methods are wrong and advise how you should be doing it. Either way how cool is this and waiting on the end number!

ptuomov

Small news:

The car can now get the boost psi up to low 20's at high rpms while still keeping the turbo shaft speed at 130k. Logging data is slow on the roads for obvious reasons, although perhaps "slow" is not the right word ... let's rather say "difficult."

It looks like there will be one final dyno data collection session before the old engine and old turbos come out and the low compression engine and the cut-weld-machine hybrid Frankenturbos go in.

A quick triangulation gives a very rough estimate of where we are on the compressor map:



"There be dragons."

123quattro

That is pretty much exactly where you want to be a for a max effort street engine.