I haven't been on the site lately with anything cool, but thought I would put this out for your review. Just found my copy of the dyno run I had October 23rd, 2006. Really interesting if you look at it. The raw numbers are okay (not great), Max. HP. 184.1, Torque 133.1 ft lbs, but take a look at the traces and tell me what you see.

I was running Al's Holley 650 DP and Racing Beat intake, stock ecu controlling ignition.

After examining the threads closely, what do you guys see and I will tell you later what the problems we discovered are.

By the way it is a 4 port 1/2 bridge with S5 internals.

Eric

 

I dunno i could be wrong on this, but looks like some heavy breakup after 7/7.5K RPM. Torque line is flat in the middle. Maybe ign issue? I seen on a friends 240 something similar, and he got himself Crane Hi-6 and cleared up the breakup and smoothed it out, not fully, but it wasnt soo choppy sorta speak. I could be way off, but thats what i guess.

 

Huge injector pump is killing low end tourque, is what me thinks

 

67 people have read this and only 2 replies???!! Come on guys.

Star is very close to the answer and Duformike is very close as well to the monster low rpm dip other than the car runs a carb, but his theory is on the right track. Hats off to both of you.

All the details are here and with some idea fleshing out you 2 guys are very close to figuring it out. It is an S4 ecu and a 650 Holley carb.

Think a bit more and if no other ideas by the end of the work day I will fill you guys in.

Eric

 

awww no AFR's to compliment this graph? or would that make it too easy? hehe

I really don't know, Im going to say you have carb. syndrome....too much too early and too little too late, then also the ignition break up of an bone stock ignition system.

Perhaps the carb can't deliver the proper amount of of fuel relative to each runner?? Its just giving the total amount and letting the air flow decide where to put it?

 

could you be getting too MUCH fuel up top? that could lead to ignition breakup as a result.
yeah, it would be a lot easier with an AFR chart, but i guess this is more fun? ha. but, i am a carb illiterate, so that's all i got.

 

does it have something to do with the jets in the carb?

 

Okay, it is a bit too hard without the AFR's. You need to understand carb theory and what the S4 ECU does to control rpm to understand what is going on. Good efforts to everyone.

This is what we think is happening.

As you can see from the chart at 3000 rpm, we were making decent power and torque. I whacked open the throttles and blaaaaah the engine falls flat on its face as the accelerator pump shot runs out. This is caused by the reduction in airspeed through all four venturi's and the reduction in vacuum in the carb to pull the fuel out of the float bowls (simplified a ton). I expected that the AFR's at that point would show a monster lean point.

As the rpm's climb the airspeed picks up and and everything runs okay to about 7,500 rpm. The AFR's in this range I expected would be about right. Good power and torque. In fact the max levels of each happen at 7,600 rpm for HP and 6,800 rpm for torque. The engine was running in its sweet spot with this set-up.

Where you see the rpm traces start to jump around and the HP start to drop the car started to run pretty rich. It made our eyes start to water. AFR's would be in the 10.1 - 11.1 range. Too much for the stock ignition set-up. I looked at the traces and it didn't make sense. There was no real misfires to cause the problem. The car revved clean, so we started to scratch our heads. Back to the factory manuals to figure out what we were seeing.

Here is what we think went on. The stock S4 controls rpm with a soft rev limiter at about 7800 rpm. We had faked the computor with a wide-open airflow meter, a TPS hooked up and not moving and an air temp switch hooked up out in the cars airstream. The controls weren't reading what was going on in the engine at all, just that it was at WOT all the time with cool air. We believe that the ecu started to implement a soft rev limiter at that time (7600 - 7700 rpm) and that the S4 does this by a combination of fuel cut off, timing reduction and primary plug shut off as the rpm's continue to grow. So basically the timing went into a limp mode initially and then stopped the primary plugs from firing. This caused the dropoff in power.

Pretty cool if we are correct because the HP and torque lines if continued on from where we think the rev limiter tried to act leads us to about 200 - 210 rwhp at around 8500 rpm. Now we are really interested in getting this hodge podge of intake and ignition stuff off the motor and putting the stand alone and ITB's on. Just got to finish off the intake first. I can see some really intense tuning sessions in January and February as we work out all the issues. The carb setup would work extremely well with the older stand alone distributor as there is no ecu to retard the timing and shut off the primary plugs. With the stock ecu, I don't think the carb gets a chance to really shine.

Does anybody here know the sequence of engine speed controls that the S4 ecu uses to limit rpm? This would really confirm what we see here.

Eric

 

makes sense because you can see the brakeup, the very fine disruption, but then further up in the RPM band it gets super extreme -10hp spikes- then the power levels, then drops off....makes sense its cutting fuel

 

Or this could all be garbage and it's running flat at that rpm because of a kinked fuel line, LOL. We don't think so though.

By the way its all effecting the ignition side only as the spikes grow in intensity the further above 7800 rpm we go.

There are no fuel system issues that we are aware of.

Eric

 

Blame it on the carb.....cause carbs are poopy that and the stock S4 ECU.......

 

I like it when you talk all hi-tech and stuff like that, Joe.

The official response from my engine builder, "carbs are poopy", LOL.

He is right though. Rich, lean, okay then rich. You really can only set them correct for one rpm and load range. All of the other ranges are compromises.

That is why fuel injection has replaced carbs and fuel/ignition mapping is so critical.

Can't wait until we get it all together. You can never have too much power!

 

Blah Blah Blah! EFI blah! A sweet tuned Weber is crisp and clean over 10,000rpm with a thing called a distributor to boot! Before we had fuel pressure problems when the holley was on my OLD engine it produced 229.6 rwhp at 9400 rpm and barely dropped off over 10,000rpm! Carbs rule!

 

Soo.............why not go with an 110 cfm tb injection kit. i bet you could piece one together with a used haltech and all the stuff to do it right for less than 2k. Tis the setup im gonna run in the vert as soon as i can get it running smoothly (brakes are toast , engine mint )

 

Hayabusa smoothed 46mm ITB's w/measured length individual runners to each port...
Walbro, Marren, etc. fuel system managed by Haltech
S4 Four-port w/stage 3 oil mods, monster bridge & hardened stationaries
S5 Rotating Assembly, Act ProLite Flywheel w/ full TII drivetrain behind it...
and more speed secrets!

All I want is to lay down faster times then you and Al

Ditch the carb!

 

You guys and your big bucks! For the price of your fuel systems I could build a peripheral port!

 

Yeah now your thinkin!

Peripheral Port with dual 55mm throttle bodies! YAY instant recipe for 300+ HP.....but only 150ft/lbs of torque.

 

I take my turbo and gizmos any day. LOL

Dam old school carbs.

 

Ah, put a nicely tuned Edelbrock on it and you'll be set. My personal opinion but so far the edelbrock on my S4 stockport has been really easy to tune. Got basic idle and light to moderate throttle tuned. Its actually really easy to tune, even myself being a beginner. But the engine falling on its face when the throttle is snapped open is definately the accelerator pump being too small. I've got that problem on my engine with stock ports. Gotta figure it out. I'm thinking a longer stroke will help solve that.

Sound like you really have things just pieced together and thats likely the source of some of your problems. I find it surprising that the holley goes real rich at high rpm. not very characteristic of a carb IMO. They don't tend to just go rich at high rpm, something else is wrong. Mabey its because the ignition was breaking up? It was probably not igniting the fuel probably and causing it to seem to run rich.

 

P.Port with a 51 Weber 300+ HP with no big buck tuning crap!

 

Ah yes, but I have documented proof that webber flanged TB's make more power than webber style carbs on a mild 13B (everything else was left the same between tests).