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View Full Version : I'm thinking I need a better fuel pump.



DriftingThunder
06-15-2005, 10:04 AM
http://www.freepichosting.com/Thumbs/421566172/32/1.jpg

After 3800 rpms it looks like the knock sensor is really busy. And can anyone clue me in as to why my torque is so much higher than my hp?

Power mods: removed air silencer, ZR Motorsports CAI (temporarily not on car because of busted motor mount), C&L/Vortec 73mm MAF, BBK 70mm TB, 3/4" raised blower outlet, double intercooler, 950cfm intercooler fan, 10% supercharger overdrive pulley, 2.25" x-pipe exhaust, Dynomax Super Turbo mufflers, and EEC chip programmed by "the man."

007_SuperCoupe
06-15-2005, 11:08 AM
Need some more information:

Did the "man" dyno tune it or just send you a chip? An actual dyno tune is the best way to go really. Otherwise its an educated guess. It would be worth the drive and money spent.

What are your intake temps like. You may not be out of injectors/fuel pump, but your intake temps could be through the roof. If that is the case, then it will take an ungoddly about of fuel to keep you from pinging. You need to know what your intake temps are so you know how efficient your IC is. For what you've listed, I wouldn't think that you'd be out of fuel...but the temps could be too high.

Next about the torque/hp numbers. Torque is naturally going to be higher because of that positive displacement supercharger on the car. (Unless you get to the point that Dave D is now with his...) I got mine dyno tuned and it came in at 248.8 rwhp/340.1 rwtq. Is that the kind of difference you are talking about? N/A engines will have numbers closer together.

lube70
06-15-2005, 01:33 PM
That 10% pulley is killing your timing. The blower hits max rpm with a 10% at about 4,200 rpm. After that, it just pulls timing due to high cylinder pressures.

I would bet that if you removed the 10% pulley, and installed a 5% or a stock one, that the numbers would be better overall except with a slight loss of low-end torque.


Don

lube70
06-15-2005, 01:35 PM
What was the air/fuel ratio???? Did the guy even bother to check it???? Usually, the O2 (wide band) sensor in the O2 bung or just the tailpipe (kinda rigged way). Either way, a air/fuel ratio is essential in knowing what's going on.

Don

DriftingThunder
06-16-2005, 01:19 AM
Well I woulda thought with the double intercooler and 950 cfm fan for it that the air temps would be... somewhat better than normal, but I definitely understand that the Eaton makes hot air. I don't know the actual intake temps though.

I don't know to what extent the car was or was not tuned, the previous owner had it done. HBK94SC was the previous owner up in Michigan. He mentioned it was tuned for 94 octane gas though. I am under the impression that it was actually dyno tuned.

Not sure on air/fuel or fuel pressure in general, but aren't the fuel pumps in these cars kinda wussy?

I still have the stock blower pulley and I've been wanting to put it back on actually. Pegging the boost gauge is fun but I understand right now it's making my car slower and just making more heat and risking headgaskets even more.

I thought it was a fuel issue because of those spikes on the dyno after 3800 rpms. Isn't that the knock sensor messing with timing? Meaning the car was running too lean up top? I also wanted to ask why the power and torque dropped as much as it did on the second pull. Is it because they only waited 11 minutes maybe? I noticed several of the spikes went away though.

Scott Long
06-16-2005, 01:48 AM
Heat soak like a bitch.

Also, it wouldn't hurt to put a 255 lph FI pump in there. And if you can find someone selling an 89-93 stock pulley, I'd say use that instead of a stock 94 pulley. Even if you spend the $60 on a 5% it will be better. Unless you have a huge front mount or an air/water IC the 10% on a late style blower is killer.

I have a 10% on my early style blower but I am also wanting to either go back to stock or go back up to a 5% since I think mine is pulling timing something fierce after about 3500 rpm. I'd gladly give up a little low end torque to get some higher RPM pull.

XR7 Dave
06-16-2005, 01:54 AM
All it needs is alcohol injection. ;)

Dirtyd0g
06-16-2005, 07:46 AM
All it needs is alcohol injection. ;)

Drinking doesn't fix anything :p

007_SuperCoupe
06-16-2005, 08:59 AM
Well I woulda thought with the double intercooler and 950 cfm fan for it that the air temps would be...

The problem with a conventional 2x IC is that there isn't a way to prevent a vast majority of the air from going into the front core. An air diffuser should be in there to even the flow between the 2 cores. That greatly increases the efficiency of the IC. Without that, a standard 2x IC is marginally better than a stock IC.


I don't know to what extent the car was or was not tuned, the previous owner had it done. HBK94SC was the previous owner up in Michigan. He mentioned it was tuned for 94 octane gas though. I am under the impression that it was actually dyno tuned.

Have you made any mods to the car since you got it? You'd be amazed at how easy it is to mess up a tune by installing one little part.


Not sure on air/fuel or fuel pressure in general, but aren't the fuel pumps in these cars kinda wussy?

Yes, they are, and considering the age, they could easily go out at about any time. Check with the previous owner to see if he changed it when he owned it. You can also check fuel pressure on the fuel rail with a fuel pressure guage. Pretty easy to do.


I still have the stock blower pulley and I've been wanting to put it back on actually. Pegging the boost gauge is fun but I understand right now it's making my car slower and just making more heat and risking headgaskets even more.

I thought it was a fuel issue because of those spikes on the dyno after 3800 rpms. Isn't that the knock sensor messing with timing? Meaning the car was running too lean up top? I also wanted to ask why the power and torque dropped as much as it did on the second pull. Is it because they only waited 11 minutes maybe? I noticed several of the spikes went away though.

Definatly a pulley change will help to get your SC performing better. A 10% on there is quite a bit on a '94-'95 SC. Dave D had difficulty tuning a '94 with only a 5% pulley on there. You could try an '89-'93 pulley to see if that helps. It should, but without much more knowledge about the workings of the car, it's really hard to say.

I'm not sure what would cause the "spikes" on the dyno. I'm not that familiar with interpreting dyno charts yet. But your second pull is lower because of heat soak. It's also possible that some tuning was done to richen the a/f ratio which could drop your power slightly, but give you a much safer ratio that won't cause as much strain on your engine...and HG's!

I'd pay the money to get it back on a dyno so you can see what the intake temps are at given rpm's as well as the a/f ratio. Especially if you've made any mods to the car since you got it. The $50 or so that you would pay to have that done can save you a lot of headache in the future. And it will give you a really good starting point to from instead of shooting in the dark.

Scott Long
06-16-2005, 03:13 PM
Say I take my car to the track and its running slower with the 10% than it was with the stock pulley on a factory tune. Now if I put in some 110 or 112 octane fuel would it make more power since the computer would still advance the timing but it wouldn't knock with the higher octane fuel, and then since I have more air coming in, would it make more power and run quicker?

I assume the alcohol injection is the same as running race fuel. You could use isopropyl alcohol instead of washer fluid. Would running water injection cool the air although not act as an octane boost?

DriftingThunder
06-16-2005, 06:31 PM
Well for now I'm selling my '86 and hoping to buy a 255 lph and a Coy Cam, and install my gear, then I'd like to meet up and tune with XR7_Dave sometime this summer.

I haven't done anything to the car since I got it except break that pesky motor mount on the passenger side. So I had to take the ZR CAI off because it'd bang on the shock tower until it popped off. So I put the stock tube back on and put the cone filter and bigger MAF on the end of it.

I have a 3.27 gear in my garage but with the wider gears in the late model M5R2 I wanted to get a 3.55. My search for a trade or cheap 3.55 is failing so I might just put the 3.27 in.

I wanna put the stock pulley back on but at the same time I wanna make the 10% work great.

David Neibert
06-16-2005, 11:09 PM
Andy,

Those look just like James Fs old dyno sheets from 2001. If they are, don't make any mods based on them...they are way too old and don't have any A/F info. Re-dyno the car and see what you've got before doing anything.

David

Scott Long
06-17-2005, 01:36 AM
That is James F.'s 94 SC that he bought. I too was worried about the shakey lines on the graph.

Also I've driven it, and in 3rd gear from about 3500 you stomp it and it just barely pulls. Takes forever to wind the gear out. So I think the car is pulling timing and killing power.

As for making the 10% work, get an NPR intercooler off ebay, we can get 'er done Andy.

Even the double's don't flow that well since they are not a double wide, just a double thick, and still blocked by an a/c condensor.

Front mount would let you run the smaller pulley.

DriftingThunder
06-18-2005, 07:29 AM
Well 68COUGAR gave me the stock early model SC pulley. I may or may not put it on because I'm possibly getting a 255 lph fuel pump order in on Monday. I mean regardless of what my car is actually doing it's a good idea to get the fuel pump am I right? I should put the stock pulley on to save headgaskets anyways though. I really dislike the M90 and knew I would. 68COUGAR wants me to be faster than him so bad, and it'll take awhile but I don't plan on using any form of M90 for longer than I have to.

Dave, it is James' car but the car hasn't changed since that dyno at all really. That dyno is old but what it reads still holds true. Scott's right on about 3rd gear it's seriously like driving an N/A 3.8L bird. Trust me, I know.

A stock 5-speed SC is supposed to do like 149 mph top speeds. My car is so slow up top I couldn't go faster than 130 mph the other night and it was pretty cold out. :( This car can go so much faster but there's some serious crap holding it back. I at least want it to show it's fangs.