Baseline Dyno Diagnostic Help Please
12-08-2005, 06:47 PM
#16
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Originally Posted by GlenL
Those HP numbers look OK.
I think the A/F is too rich. Bad numbers from the sensor? Maybe someone has a comparable chart to post.
I think the A/F is too rich. Bad numbers from the sensor? Maybe someone has a comparable chart to post.
12-08-2005, 07:07 PM
#17
Nordschleife Master
Yes, too rich.
The A/F ratio that gives the most power from an engine is 12.5:1. This is, of course, a theoretical number derived from looking at the heat obtained in the reaction. It's on the rich side so all O2 is consumed. There's lots of unburned CO left over but the overall reaction have yielded more power.
Here's a graph that give the idea:
http://hurricane-horsepower.com/images/af-emissions.gif
When I last dyno'd my CIS car the best power was near 13.7:1. Going richer was a loss of power. I'm not sure about the accuracy number, but the dyno graphs were what was important.
I'd be surprised if a stock engine would go below 13.5 as the emissions numbers get ugly. That's why I'd like to see another car's run.
The A/F ratio that gives the most power from an engine is 12.5:1. This is, of course, a theoretical number derived from looking at the heat obtained in the reaction. It's on the rich side so all O2 is consumed. There's lots of unburned CO left over but the overall reaction have yielded more power.
Here's a graph that give the idea:
http://hurricane-horsepower.com/images/af-emissions.gif
When I last dyno'd my CIS car the best power was near 13.7:1. Going richer was a loss of power. I'm not sure about the accuracy number, but the dyno graphs were what was important.
I'd be surprised if a stock engine would go below 13.5 as the emissions numbers get ugly. That's why I'd like to see another car's run.
12-08-2005, 07:17 PM
#18
Drifting
In our X-over post, the first dyno chart is the 86.5' 5-speed stock, with the Ott and with our X-over. The car gets a bit leaner each progression but it is a good running example of factory stock air/fuel ratios. When I added our 2.5" cat back system it went way too lean and only gained another 4 hp.
https://rennlist.com/forums/showthre...ghlight=rabbit
https://rennlist.com/forums/showthre...ghlight=rabbit
12-09-2005, 10:49 AM
#19
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Ok, so from what I gather the car is running rich and if I were to play with it I may be able to get another 10-20hp out by adjusting the fuel and running it in 3rd gear. I was hoping to be in the 250-260 hp range. If I were to play with it I should be able to get it, but the baseline run is close enough and it looks like the car is in the ballpark to start the SC install.
For the SC install I plan on leaving the fuel as is and going back to the production chip for the initial runs (3rd and 4th gear) as a safety factor. Then leaning it out to get better numbers. From what I understand I should not use aftermarket chips with the SC installed???
For the SC install I plan on leaving the fuel as is and going back to the production chip for the initial runs (3rd and 4th gear) as a safety factor. Then leaning it out to get better numbers. From what I understand I should not use aftermarket chips with the SC installed???
12-09-2005, 11:06 AM
#20
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I may be able to get another 10-20hp out by adjusting the fuel and running it in 3rd gear
Most will use 4th on a 5 speed since it is closest to the 1:1.
5th is ideal, but most dyno operators won't run the 2.20 rear in 5th since it's over 200mph.
The longer the run, the more data can be collected.
12-09-2005, 05:17 PM
#23
Rennlist Member
dynojet more closely approximates our driving conditions, race or street. the problem here is the correction factor. thats why i always use the ACTUAL data as well. that way , you can decide based on condtions if the drop in HP is actually 20hp or not. (for a standard day) .93 works out to 265hp at the wheels, probably pretty close to what a stock S4 would make, right, so it looks like your car is in the right range for a stock 86. your ratios look a little rich. how did you get them in this area???? usually the S4s are dangerously close to the 14:1 range!
the dip at 3k is normal though. flappy seems to be working too!
mk
the dip at 3k is normal though. flappy seems to be working too!
mk
Originally Posted by Herr-Kuhn
Don't sweat it too much. Correction factors and the like can take their toll on the results. I've never been a big fan of the dynojets. Regardless of what people say there are variances in the results. You are off like 20 or so HP...not the end of the world.
12-09-2005, 05:20 PM
#24
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I always use 4th. but, one time i used 3rd by mistake and the difference was a solid 4hp from top to bottom. as said, the closer you get to 5th gear, the losses are reduced.
Mk'
Mk'
Originally Posted by John Veninger
You don't "gain" HP by using a different gear!
Most will use 4th on a 5 speed since it is closest to the 1:1.
5th is ideal, but most dyno operators won't run the 2.20 rear in 5th since it's over 200mph.
The longer the run, the more data can be collected.
Most will use 4th on a 5 speed since it is closest to the 1:1.
5th is ideal, but most dyno operators won't run the 2.20 rear in 5th since it's over 200mph.
The longer the run, the more data can be collected.
12-09-2005, 05:23 PM
#25
Rennlist Member
you wont see too much change in the hp going from your rich 11:1 range from 5k to 6k vs going to 12.5:1 as you have at 4000rpm. we did similar tests with my 5 liter and the difference was less than 5hp when we optimized at around 12.5:1. however, the leaner you go passed the 13:1 range, you can see some dramatic hp loss changes, espcially on the other side of Stoich (ie 14.7:1) But, this is not the problem here!
mk
mk
12-09-2005, 05:51 PM
#26
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Thread Starter
your ratios look a little rich. how did you get them in this area????
Mark, I have a very old adjustable fuel pressure regulator and an ARM-1 installed. I cranked up the fuel pressure until I hit the last blue light (12.5:1) when I was at WOT this past summer.
Mark, I have a very old adjustable fuel pressure regulator and an ARM-1 installed. I cranked up the fuel pressure until I hit the last blue light (12.5:1) when I was at WOT this past summer.
12-09-2005, 06:18 PM
#27
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why i always use the ACTUAL data as well
Using actual doesn't allow for that unless the temp. and pressure is the same, then you have a proper comparison between your runs, not someone elses
I'll go out and use actual tonight at the dyno. What do you think I'll get for numbers with the air at 19.
Corrected (with the dyno operator not playing with the correction) is the best way to compare performance.
12-14-2005, 03:28 PM
#29
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Originally Posted by GlenL
Yes, too rich.
The A/F ratio that gives the most power from an engine is 12.5:1. I'd be surprised if a stock engine would go below 13.5 as the emissions numbers get ugly. That's why I'd like to see another car's run.
The A/F ratio that gives the most power from an engine is 12.5:1. I'd be surprised if a stock engine would go below 13.5 as the emissions numbers get ugly. That's why I'd like to see another car's run.
12-14-2005, 04:36 PM
#30
Rennlist Member
Check your cam timing, if it's off even a little you can lose significant hp. My 85 made 291 rwhp, mods were Cloutier exhaust, heads ported, ARRFR, SMT-6 piggy back and 19 pound injectors with idle fuel pressue at 2.5 bar.