dprantl

Unless Mark's EZK is retarding ignition timing because of excess knock or there is not enough advance, sharktuning will not do anything for him. He already said that he dialed in the AFR to be leaner and didn't get much difference. The only other thing the sharktuner can do is change the amount of fuel the injectors are producing that will change the AFR, which Mark can already do.

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

GregBBRD

I studied Carl's spacers carefully, when they were bolted onto the manifold they were going to be on. This manifold was for a 6.5 engine...and I did a tremendous amount of work to the manifold. I wasn't too pleased with the "square" edge that the air "saw" with the spacers in place. Therefore, I did a bunch of smoothing and cutting on the spacers, while they were screwed down, in place. I think Rob Edwards posted pictures of this, on his thread about his engine.

I've not had a set of Roger's spacers in my hand, much less on an intake, but I'm going to guess that they might have the same "square" edge issue.

We have not dynoed the engine that these are on, yet. Just picked it up at the exhaust shop. It has not been tuned, yet. It is still in the "break-in"period...which means we are avoiding full throttle applications and are not running it over 6,000 rpms. However, we have driven it, some. It is certainly the best engine we have built, to date.

It is...how do I word this???? A bad ***.

ROG100

Greg,
What do you think the effect will be on a stock engine - say a 90S4?
Appreciate your comments please.
Best,
Roger

GregBBRD

Roger,

I really don't know the answer to that. Stock manifolds certainly define the power as the engines get bigger, but GTs and GTS engines made pretty good power gains from basically the same manifold as on a S-4.

IcemanG17

Greg
The amount of custom porting you put in that intake is incredible...that had to take many hours to get the intake looking like that......it will be great to see how it compares to other strokers you have built with stock intakes or even the CF intake Joe and Mark run...

Since its installed on the car right now, its not really practical to hook it up to your flow bench to get some #'s from it...then you'd have some hard data as to flow gains!!

928SS

I'm not sure a bench can predict performance very well... like sterling noted, there are lots of parameters in play, just opening up a port doesn't always mean more power unless the other components are already limited by it.

could be that the eram already pushs enough air into the system that the extra spacing doesn't matter. or the edges are goofy, or injectors were maxed out, or, or....

ptuomov

Your bad-*** engine is of course a result of a large number of carefully thought-out changes to the stock engine. With your experience, it's not surprising that the engine rocks.

However, in the interest of science, I have to ask: Are you planning to run this new engine back-to-back with your ported manifold and with a stock manifold?

ptuomov

The short-runner ITBs are a clear and unambiguous improvement, based on both data and logic. This is not in question.

However, I have heard of about as many dyno experiments in which the overbored throttle body in the stock S4 manifold marginally reduced the maximum power as I've heads of increases.

Now we have a couple of data points on the spacers for and against. It seems that Kibort's experiment was a reasonably comparable to his base case experiment.

So, I agree that there may be combinations in which these parts help, but in a typical stroker or stock engine, they don't reliably produce a max power increase. To get further than that, we would have to get very detailed data about each engine on which the tests are run to try to understand which combinations (if any) play well together.

mark kibort

This is not entirely true. my 84 went through the same tuning that ive done here. 4.7 170rwhp baseline, 12hp for headers, 12hp then for open exhuast with good Y pipe, 40hp for euro cams and intake/TB/plennum. tuning from 13.5 to 12.5:1 fuel air gave the last 3hp. advancing timing 5 degrees took away 2hp so we put it back to stock.

The holbert car went from 290rwp to 335rwhp with headers and fuel regulator.
fuel just helped get things in the safe area, but no real HP gains were seen.
the engine lasted 7 racing seasons, more than any 928 engine to date.

Now, we have the stroker, ran on a dyno jet, fuel looked fat. leaned it out a bit and got 365rwhp. went to another dyno with the fuel leaned some more, it went to 372rwhp, but that with timing retarded to "0" from 8 degrees advanced. Lost 10ftlbs of torque, which was fine for the shape of the HP curve and torque curve, as the losses were near post shift points.


NOW, i go put the intake plates and lose 30ft-lbs of torque all the way to 5000rpm and a little more 'til 5700rpm. Im thinking they are doing something bad to the flow. who knows. lots of factors. However it wasnt like the entire curve was shifted up or down, it was a clear loss in a specific area. max HP is still the same.

I also measured fuel pressure, it seems that the RRFR cant really get the pressure down passed 42psi. I think the 24lb injectors were probably the way to go, as i kind of like higher pressure anyway.

There we go. If it hadnt been for the rise in fuel ratio, it might have been a closed case. with the dramatic fuel ratios, there is a few questions. Im not convinced either, but the fact that i also leaned out the ratios at the dyno, and it did nothing to the massive 30ft-lbs loss, i have to suspect that the spacers could cause some problem with the resonance plennum. Keep in mind, the losses are exactly in the area that the flappy being open vs closed would happen. with the flappy closed, the same kind of loss happens. maybe the spacer counteracts its fuction. ????????????????

mk

Hilton

It seems that with all this debate, the state of tune is the large difference. Changing the air path, velocity, and flow characteristics all impact the tune through things like resonance waves, atomisation differences, speed of cylinder filling, relative differences between cylinders etc.

Porsche optimised the tune for characteristics they wanted from the engine in the car, relative to the stock components.

The only conclusive approach would be to have someone with a sharktuner, and a repeatable process for sharktuning, optimise an engine without, and then again with, the changes under consideration. Whether it be porting heads, redesigning intakes, changing headers etc.

Unfortunately, that puts a massive cost and burden on the process to be borne by developers, and the pool of people who could be applied to that approach to tuning a 928 is very small (Greg Brown, Jim Morton, Tim Murphy, John Speake, Louie Ott um.. that might be about it?).

So the alternative is different enthusiasts try out ideas on their own unique setups, and under unique conditions - and we find that for some there's a gain and for others there isn't. The net outcome is that solutions like X-pipes that show a consistent gain become widespread and accepted, and other stuff is debated.

Having looked at some of the very helpful information provided by Hacker on behalf of Todd, to do with which cylinders run leaner/richer with the stock manifold, logic says spacers should help - but the cost of testing in other-than-stock configuration is high!

Arguing about whether they do/don't work in general seems to be besides the point? If they provide a provable gain for some cars, then there is obviously a potential gain available, and others should be asking why?

Mark, get your car tuned dammit :P

Reminds me, I need to book a dyno session for my '89 so I can take along my x-pipe for a before and after to satisfy my own curiousity.

Thanks to Mark, Brian, Sterling and others who've posted dyno sheets and information about modifications!

IcemanG17

Hilton
You bring up some EXCELLENT points.....which also reminds me to get sharky tested with the X pipe....it appears this mods tends to give around 20+whp...but given the already high #'s sharky puts down I would be happy with anything over 300whp or a 14whp gain.....just got to get sharky to the dyno....

mark kibort

Thats a common misconception of the tuning done with a fuel regulator. sure, shark tuning will optimize the fuel in all areas, but if you get it in the right range with the RRFR, you can have moments of glory along the way. with a race car having such a narrow operating range, i dont think optimizing fuel from very rich to properly rich will house mega hp. a lot of S4s run very lean, there are bigger gains going from lean to 12.5:1. tuners will tell you and books have been written, that real rich vs safety rich might not hold too much in the way of gains. As it is, i have not lost any HP. But losing 30 hp and 30ft-lbs of torque in the mid range is a little interesting. by the way, when I did try to lean out the fuel mixture, it did sense that it leaned out a half a point. hp and torque didnt budge at all. had I got a little hp movment, I would have continued my leaning out. I think the 30lb injectors cant flow any less with the regulators seeming hitting a low limit of 42psi.

No tuning at all? Did anderson have any tuning when he went from 420 to 500rwhp? Fan? stock ecus, no shark tuning, and lots of gains.
On the shark tuning side, i have a friend with a stroker BUT the big valve heads that went from 390 to 420 with fuel. It started out lean, and ended up a little fat. It had some idle issues and some shop just tweeked the mixture to idle specs and tossed most of the dyno tune out the window I imagine.


mk

mark kibort

By the way, I have the devek equal length headers , their tuned y pipe with a 3.5" straigth pipe all the way out to a 3.5" borla tip.

I also forgot to add many thanks to Roger to send me the parts for test. If we can figure out a way to make them work, or specific tuning to take advantage of the intuitive gains they should make, I will try them again.

MK

GregBBRD

Well, sort of...

Shaun Smith's engine is a virtual duplicate of this engine, with slightly milder exhaust cams....and a couple of other small changes. He is bringing his back in for the 1000 mile checkover and we are going to put the same cams that are in this new engine into his. We will then retune his engine and have a pretty good comparision. His engine is "slightly detuned", right now..to help break-in.

I don't expect this intake to equal a complete custom intake like we have "sitting on the shelf", but I'd be surprised if it didn't wake things up, considerably.

GregBBRD

I think you might be taking the "no tuning" part of Joseph's and Mark's engines too literal. There are many things that can be done, without using a Sharktuner, to achieve goals. They might want you to think that these engines are "untuned", but that might not reflect exactly what is happening.