Dyno results

rs911t · 06-07-2003, 10:25 AM

Disappointing to say the least. The 1st owner and fellow that worked on the engine say it should be 220-235 at the crank.

I clearly have some work to do. My first guess is ignition. A couple other things became apparent. First, my tach is off. Second, the MSD unit's rev limiter kicks in around 6800 rpm when the engine's redline is 7200. I've been suspicious of my distributor for a while - timing has been hard to set.

Thougts?

nostatic · nostatic's Garage

if they predict 220 at the crank, you should be seeing maybe 190? Seems like it might not be too far off it you could get to higher revs.

Also, how many runs were done? "one" is not statistically relevant...

rs911t · 06-07-2003, 10:33 AM

2.4L case turned into 2.8L with addition of RSR P/C, S heads, S cams, Webers, 7200 rpm redline, MSD with Crane ignition, 10.5:1 CR, single plug running 110 race gas during the test.

nostatic · nostatic's Garage

well, if you extrapolate that hp curve (with the peaks), if you got near 7200rpm you should be close to 200hp.

Seems like just some tweaks needed. I'll bet it is a fun car as-is though...

sithot · 06-07-2003, 10:40 AM

The distributor, points gap and timing will cause more problems than you might guess. I'd go that route first. You might also consider a compression test as well as a leak down to see if all cylinders/heads are in good order.

Good luck.

rs911t · 06-07-2003, 10:43 AM

Nostatic, good point - I hadn't extrapolated. That's a good sign! Yes, it is a fun car to drive...

Jim Richards · 06-07-2003, 11:01 AM

And it's good looking.

briankeithsmith · 06-07-2003, 12:36 PM

I've ridden in that car, and instructed Greg and that car does not feel like it is low on HP. The thing is a blast.

Not to mention that the owner knows how to drive the thing...

Brian

Stanley · 06-07-2003, 01:23 PM

It could the dyno too. When the Mistu Evo's first came out in the US everyone wanted to know what the wheel HP was and when they were tested there was a huge discrepancies on different dynos (like 40+ hp). A better indication of your HP is testing the car without the mods, then with them at the same shop. However, if the butt dyno tells you its fast, then be happy with it. Do you really need a # to confirm that you car is fast?

VincentVega · 06-07-2003, 01:33 PM

The car sounded great on the straight at Summit, as you passed me.

rs911t · 06-07-2003, 05:13 PM

I was most surprised by the peakiness of the graph. The few cars before mine had nice, smooth graphs, so I'm sure the dyno was working fine. I really wasn't looking for a # so much as an empirical indication of engine health. Tweeks are in order. Maybe I need different color plug wires ...

06-07-2003, 05:31 PM

I think you should have turned on the stereo! That gave me at least another 5hp.

CamB · CamB's Garage

I agree you are down a bit on power. My flavour of the month for dyno conversion is the 167, plus 10hp ('cause of the wheels/tyres etc), then times 1.15 (or /0.87 - 13% loss). Gives you about 200hp.

I would guess (with no qualification or expertise) that you should see 230 or so as well.

If you want to try stuff, I found that my BMW (Bosch distributor, MSD 6AL) was bringing in the MSD rev limit anywhere from 600rpm to 1000rpm too soon.

It appears it is due to points bounce, which is only a problem because the distributor seems to be worn, which means that the dwell changes with RPM (to the point where it closes up so much that there is a problem with bounce). This even happened with a stiffer set of points.

Easy to check - hook up the dwell meter and rev the engine.

Wil Ferch · 06-09-2003, 06:18 AM

As I've mentioned before....are the results "raw" data, un-corrected to SAE atmospheric standards...or were they SAE corrected? May result in a BIG numerical difference, since SAE takes the raw data, and corrects to standard set of conditions ( 70 degF, sea level, 50 % RH). Done this way, I've seen identical cars at two locations come very close together in results.
--Wil Ferch

ttweed · ttweed's Garage

Quote:

Originally posted by Stanley
... there was a huge discrepancies on different dynos (like 40+ hp).

This is absolutely true. I have seen differences of 20+ HP reported on the same engine using a Dynojet vs. Dyno Dynamics machines, even when corrected to SAE standards. Differences for Mustang dynos are supposed to be even larger. What kind of dyno was this?

Quote:

originally posted by Greg
I was most surprised by the peakiness of the graph.

Did the shop give you a printout of your A/F ratios? Look for your mixture going too rich in the RPM range where the dips are.

TT

rs911t · 06-09-2003, 09:21 AM

Tom,

The dyno was a Mustang nor did they provide any other info. It was a PCA charity gig. My current theory is that (1) they were using an RF sensor for rpms since nobody got into the engine compartment and (2) my MSD caused screwy rpm readings. I'm waiting a call back from the shop.

Mr Beau · 06-09-2003, 10:14 AM

Greg,

I wouldn't be worried about the lack of power, but the peakiness of the graph. It almost looks like the engine was misfiring, but I'm sure you would have heard it if that was the case.

Mustang dyno's typically read less than Dynojet's, and due to different ways they measure power, it's basically impossible to compare them using a formula. It's also basically impossible to convert either one back to crank HP, which is how the factory rates them. They are good for checking increases/decreases and providing "reality" checks, but not for obtaining "absolute" numbers.

When you say they were using an RF sensor since they didn't go in the engine compartment, do you mean they didn't put any sensors on the plug wires? If this is the case, any ignition problems you may have had would not have affected the results as the RPM would have been taken form the drums.

You may want to go through you ignition system to make sure everythign is OK, and then head back to a dyno facility with a wide band O2 sensor to ensure everything is set properly.

Good luck...

Matt

rs911t · 06-09-2003, 10:27 AM

Matt, thanks for the info. RPM info from the drums would also be wrong, since I don't have stock gearing. Mustang sells an RF sensor (as well as the usual inductive stuff) with their software package to capture rpms.

I'm not worried about power, either. The car sounds and runs well, though I am going thru the typical ignition tune-up things. As far as sound and how it runs, below is a video from a recent track day. It was running pretty well!

http://demoware.adrenaline.com/english/pub/one-lap-summit-point2.mpg

speeder · speeder's Garage

Greg, I'm no expert on dynos, (just know what I've learned here), but I agree w/ the others about the unreliability of those raw #s. The thing that would concern me is the peaky graph, something is definitely not right if the other cars had a smooth graph. (Not the machine malfunctioning).

pwd72s · 06-09-2003, 10:58 AM

Quote:

Originally posted by briankeithsmith
I've ridden in that car, and instructed Greg and that car does not feel like it is low on HP. The thing is a blast.

Not to mention that the owner knows how to drive the thing...

Brian

I've ridden in that car too. Of course, it was a few years ago...

and it wasn't down on power then, either!