Supercharger Dyno: Too Rich or Too Lean?
05-01-2001, 05:11 PM
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Help with my dyno please... looking at the air/fuel ratio above 6000 rpm, am I running too rich or too lean? Do I need more fuel or not? My dyno was a little disappointing and am trying to tune the car a bit.
After all of my mods, I expected a bit more HP... it seems ANY mod in addition to the supercharger is completely transparent...
Thanks for any help!
After all of my mods, I expected a bit more HP... it seems ANY mod in addition to the supercharger is completely transparent...
Thanks for any help!
05-01-2001, 05:34 PM
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That is kinda a bummer. Waht "mods" do you have? I know numbers between dynos' can vary but I thought comptech was claiming closer to 300 BHP with these mods. Hmmmmm maybe your engine was bilt on a Monday! I am sure the supercharger is a blast and I am interested in it, but it is dissapointing to see the difernece in actual numbers.....escp when ya drop the $4000
just my 2 cents
Please nobody get mad and bent out of shape!
Thank you , and have a pleasant day/night
just my 2 cents
Please nobody get mad and bent out of shape!
Thank you , and have a pleasant day/night
05-01-2001, 06:04 PM
#4
shaner, looks good to me?
Don't sweat the numbers, leave that to the BENCH RACERS
you know how fast your sh!t is.
Looks lean overall however (would have expected something in the 12-13 range, maybe the scales off on the chart
.
Also, if your ECM sees the Intake Air Temp above ~160 F it's rumored you get dialed back in the timing dept. Mine gets to 170 F pretty easy if I idle through a parking lot for couple minutes before getting back on the road. You can definitely tell the difference (butt-dyno) until you get the heat soak out.
Are you running stock computer?
What MAP sensor treatment you using?
Don't sweat the numbers, leave that to the BENCH RACERS
you know how fast your sh!t is.Looks lean overall however (would have expected something in the 12-13 range, maybe the scales off on the chart
.Also, if your ECM sees the Intake Air Temp above ~160 F it's rumored you get dialed back in the timing dept. Mine gets to 170 F pretty easy if I idle through a parking lot for couple minutes before getting back on the road. You can definitely tell the difference (butt-dyno) until you get the heat soak out.
Are you running stock computer?
What MAP sensor treatment you using?
05-01-2001, 07:38 PM
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[QUOTE]Originally posted by RT
[B]shaner, looks good to me?
Don't sweat the numbers, leave that to the BENCH RACERS you know how fast your sh!t is.
Looks lean overall however (would have expected something in the 12-13 range, maybe the scales off on the chart .
Also, if your ECM sees the Intake Air Temp above ~160 F it's rumored you get dialed back in the timing dept.
[B]shaner, looks good to me?
Don't sweat the numbers, leave that to the BENCH RACERS
you know how fast your sh!t is.Looks lean overall however (would have expected something in the 12-13 range, maybe the scales off on the chart
.Also, if your ECM sees the Intake Air Temp above ~160 F it's rumored you get dialed back in the timing dept.
05-01-2001, 09:10 PM
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Hi Shaner,
I had my car at Comptech a couple of days ago and got very similar HP readings on their chasis dyno. Q: Did you take the RPM up to the rev limiter or did you let off before? If you let off before you could have easily seen an extra 4 to 5HP by going a little further. The table i have shows 283HP @ 8800RPM with a max torque of 174.4FtLbs @ 7600RPM.
Your AFR does look a bit high compared to mine, though i'm told by Shad @ Comptech that the exhaust probes used are rather inacurate. My AFR shows 10.6 @ 8600,5800,3800 RPM. These readings are a fair bit lower then yours except at 1600RPM where i'm seeing a value of 14.4
I recently bought one of these guys http://www.obd-2.com
It shows IATs of 20F to 30F above a NA car, with my car showing around 160F and Josh3io's car showing about 140F on the same day not far apart.
SilverSurfer's car has dynoed about 10HP more then mine, we atribute this to his Comptech exhaust... though i guess it could be something else...
I had my car at Comptech a couple of days ago and got very similar HP readings on their chasis dyno. Q: Did you take the RPM up to the rev limiter or did you let off before? If you let off before you could have easily seen an extra 4 to 5HP by going a little further. The table i have shows 283HP @ 8800RPM with a max torque of 174.4FtLbs @ 7600RPM.
Your AFR does look a bit high compared to mine, though i'm told by Shad @ Comptech that the exhaust probes used are rather inacurate. My AFR shows 10.6 @ 8600,5800,3800 RPM. These readings are a fair bit lower then yours except at 1600RPM where i'm seeing a value of 14.4
I recently bought one of these guys http://www.obd-2.com
It shows IATs of 20F to 30F above a NA car, with my car showing around 160F and Josh3io's car showing about 140F on the same day not far apart.
SilverSurfer's car has dynoed about 10HP more then mine, we atribute this to his Comptech exhaust... though i guess it could be something else...
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05-01-2001, 09:26 PM
#8
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O.k., first let me say that the A/F ratio measured here may not be totally accurate. If you measure after the cat, you introduce some error into the measurement. However, the error should be consistent, and the curve is shaped like I would expect a stock fueling curve to be shaped. Notice how the curve rises and falls exactly in sync with what the stock torque curve looks like - peak at 3200-3300, drop to 4200-4300 and back up again. Another reason why you really want to reprogram injector pulsewidth for an FI engine, you don't need that anymore because the charger is masking much, if not all, of the resonance issues in the intake manifold. If you were running the car stock, you probably wouldn't see much in the way of A/F change through that range. I also am encouraged by how rich the car gets up top (relative), means that us NA guys should indeed pick up a lot of power with some leaning as some have reported.
All that said, if the actual ratio is anywhere close to what is shown, you're running too lean. The consolation is that you get richer up high, which is useful in prolonging engine life :-). You're above 14:1 all the way until 8000 rpm, and even then you don't go much lower than 13.5:1 at best. Running a car near stoich (14.7:1) or above at full throttle, especially a blown motor with higher than normal intake temps, is asking for trouble. Stoich assumes all the fuel particles find all the free air molecules and they all combust nicely. In reality, that doesn't tend to happen because the mixture isn't perfectly homogenous. Thus, you need to make sure you have some extra fuel in the chamber because you want to make sure you use all the oxygen. If you don't, all that oxygen is going to look for something else to oxidize (read burn) and that ends up being a valve or a piston.
Additionally, lean mixtures run hotter (to a point) which can increase your chances of detonation. Something else you don't want, even with a knock sensor to protect you.
As a reference, on my 7 psi, 9:1 motor we measure A/F ratio on the leanest cylinder a few inches from the exhaust port using a wideband O2 sensor. We have a fully programmable ECU so we can alter timing and fuel pulsewidth almost infinitely and on the fly. We found that we tended to get best power right near 13:1, but we started getting hints of detonation in higher gears (4th). We backed it off to about 12.7:1 and the car runs beautifully with good temps, etc. We stay between 12.6 and 12.8:1 across virtually the entire rpm range, adding just a big more fuel before the rev limiter.
From the looks of your graph vs. others like Jim's (SCS2K) you look pretty normal on power until very high rpms. Then it looks like something has stepped in and cut off the last 500 rpms of the curve. Do a search for Jim's old chart and take a look, but I believe his power kept going up right to the limiter. Perhaps you detonated somewhere in there and the ECU pulled out timing? Or maybe intake/engine temps were getting too hot so, again, the ECU pulled out timing. It doesn't look like the richer mixture up top really hurt you because the A/F ratio bottomed past 8000 and torque didn't turn over till about 8300.
If you can, check your OBDII system and see what the knock sensor has been reading. The laptop OBDII scantool programs available should be able to track that and look at any freeze frame references. You may have to run the car up to the redline with the tool hooked up while datalogging the knock output. If you don't see any signs of knock, then I doubt the mixture is actually lean.
BTW, what other mods do you have? That could certainly be impacting performance. You'd be surprised how some little thing can screw up everything else. Also, what gears were the pulls made in? Conditions? Smoothing factor on the graph? What model dynojet? All these things are useful to know.
UL
All that said, if the actual ratio is anywhere close to what is shown, you're running too lean. The consolation is that you get richer up high, which is useful in prolonging engine life :-). You're above 14:1 all the way until 8000 rpm, and even then you don't go much lower than 13.5:1 at best. Running a car near stoich (14.7:1) or above at full throttle, especially a blown motor with higher than normal intake temps, is asking for trouble. Stoich assumes all the fuel particles find all the free air molecules and they all combust nicely. In reality, that doesn't tend to happen because the mixture isn't perfectly homogenous. Thus, you need to make sure you have some extra fuel in the chamber because you want to make sure you use all the oxygen. If you don't, all that oxygen is going to look for something else to oxidize (read burn) and that ends up being a valve or a piston.
Additionally, lean mixtures run hotter (to a point) which can increase your chances of detonation. Something else you don't want, even with a knock sensor to protect you.
As a reference, on my 7 psi, 9:1 motor we measure A/F ratio on the leanest cylinder a few inches from the exhaust port using a wideband O2 sensor. We have a fully programmable ECU so we can alter timing and fuel pulsewidth almost infinitely and on the fly. We found that we tended to get best power right near 13:1, but we started getting hints of detonation in higher gears (4th). We backed it off to about 12.7:1 and the car runs beautifully with good temps, etc. We stay between 12.6 and 12.8:1 across virtually the entire rpm range, adding just a big more fuel before the rev limiter.
From the looks of your graph vs. others like Jim's (SCS2K) you look pretty normal on power until very high rpms. Then it looks like something has stepped in and cut off the last 500 rpms of the curve. Do a search for Jim's old chart and take a look, but I believe his power kept going up right to the limiter. Perhaps you detonated somewhere in there and the ECU pulled out timing? Or maybe intake/engine temps were getting too hot so, again, the ECU pulled out timing. It doesn't look like the richer mixture up top really hurt you because the A/F ratio bottomed past 8000 and torque didn't turn over till about 8300.
If you can, check your OBDII system and see what the knock sensor has been reading. The laptop OBDII scantool programs available should be able to track that and look at any freeze frame references. You may have to run the car up to the redline with the tool hooked up while datalogging the knock output. If you don't see any signs of knock, then I doubt the mixture is actually lean.
BTW, what other mods do you have? That could certainly be impacting performance. You'd be surprised how some little thing can screw up everything else. Also, what gears were the pulls made in? Conditions? Smoothing factor on the graph? What model dynojet? All these things are useful to know.
UL
05-02-2001, 04:04 AM
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Guys,
Thank you all for your replies and VERY useful insight... let me add some information:
My modifications are:
-Bored TB
-Extrude/Honed Intake manifold
-Mugen headers
-BYS straight pipe... no catalyst
-Comptech exhaust
-Mugen ECU <-- no engine retarding due to environmental elements
-My custom dual-filtered cold-air intake... which I traded with the Comptech 'stock' box... both gave identical dyno readings.
-I am using the GhostBooster ECU fix
-This was a dyno run after letting the car cool to 2 bars
-Approximately 65 deg F
-4th gear
-Dynojet Model 248 Dynamometer
Does anyone have any "real" numbers on the few air/air intercoolers running around?
Thank you all for your replies and VERY useful insight... let me add some information:
My modifications are:
-Bored TB
-Extrude/Honed Intake manifold
-Mugen headers
-BYS straight pipe... no catalyst
-Comptech exhaust
-Mugen ECU <-- no engine retarding due to environmental elements
-My custom dual-filtered cold-air intake... which I traded with the Comptech 'stock' box... both gave identical dyno readings.
-I am using the GhostBooster ECU fix
-This was a dyno run after letting the car cool to 2 bars
-Approximately 65 deg F
-4th gear
-Dynojet Model 248 Dynamometer
Does anyone have any "real" numbers on the few air/air intercoolers running around?
05-02-2001, 08:09 AM
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Hmmmm, I Have the ProFlow TB bore and the GhostBooster as well. I'm also using 10-40 Readline Motor Oil, my butt dyno seemed to notice an improvement with this oil and there was an improvement of about 5HP between oils... but thats measured on 2 different dynos.