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I'm curious as to how this group feels about so claimed dyno records, correction factors, and the level of scrutiny that should be given when claims are made.
This is also meant to be educational and informative for all involved.
Also, how do you feel when you see dyno numbers posted and then the car never backs up those "posted" numbers?
Feel free to post up your thoughts, questions, examples, and even real world experiences.
No one knows what happens to the reported SAE dyno numbers if the dyno operator enters the barometric pressure as being lower than actual on the day of the test?
Ben, on my 4 mustangs, and my first 2 corvettes, I used 3 dynos.
Mustangs-Strictly Performance
Corvettes-England Green and Gforce
I drove the car directly to the track after these pulls either that Friday night or for a track rental before TSS. I kept all my time slips which is a huge stack, but most numbers are faded.
I loved dynos when I would drag race almost weekly(besides the summer). Using the same dyno and correction factors was great to see what the car would MPH. I found all three shops dynos to be accurate according to my gains there vs the MPH.
The only pass I can't figure out was at a track rental when I ran my C6 on a Novi 1500. The first pass, off the bottle was 149+mph. The bottle wasn't in the car, the nitrous hadn't even showed up to the track from Gforce. The 60ft was down, not because of wheel spin, but because I didn't want to break the first pass on the stock driveline. Here were the non nitrous passes of the day.
Then here were the nitrous passes.
Granted, the car made 860 on nitrous and 820 off it on this tune. The DA didn't change much through the day. So why was my highest trap off the bottle, then my other 9 second passes were 142-144, including other days? It's not like that was my first rodeo. No changes made to the car that day. 149 at 820rwhp with a 6 point, roll bar, a suitcase in the trunk, no drag wheel setup, full street trim. This one I can't figure out. I've discussed this with Alan.
Long story short, I love adding mods on the same dyno, going strait to the track and seeing the difference.
Those back to back 9.81's were funny. Also to note, the nitrous was turned on at different times in the two runs. It was a switch behind the shifter. I missed 3rd gear first pass turning it on at the top of 2nd. I got it the second pass. Mikey wanted me to launch off it and run a 9.3-9.4. I had a trip to go on driving the car from the track and refused.
Last edited by winters97gt; 04-14-2017 at 12:08 AM.
Dynos are certainly a good tuning/diagnostic tool, and when used with the SAE correction, a general "ball park" for comparison purposes, but ultimately, trap speed doesn't lie... granted there is a ton of variables that affect trap speed, and even more that effect ET, but generally speaking, if the car is setup right and geared right, the trap speed/weight/DA equation pretty much tells you your true HP...or at least the HP that counts.
I've seen so many 1000-1200 rwhp cars trapping 150 mph and I just SMH...
I will agree though that BIG hp cars will show the HP/MPH more on longer tracks where there is more time/distance to make up for lack of traction and efficiencies.
Dynos are certainly a good tuning/diagnostic tool, and when used with the SAE correction, a general "ball park" for comparison purposes, but ultimately, trap speed doesn't lie... granted there is a ton of variables that affect trap speed, and even more that effect ET, but generally speaking, if the car is setup right and geared right, the trap speed/weight/DA equation pretty much tells you your true HP...or at least the HP that counts.
I've seen so many 1000-1200 rwhp cars trapping 150 mph and I just SMH...
I will agree though that BIG hp cars will show the HP/MPH more on longer tracks where there is more time/distance to make up for lack of traction and efficiencies.
When I first dyno'd 1021whp, I got a lot of crap from people in the background saying it was BS. I went to 5 other dyno's throughout the DFW metroplex, dyno'd 1000+ at each site and drove home. When I started track tuning my car, I was able to run 151 in the 1/4, but one very significant thing that I discovered is that gears 1 through 3 were lean. I tune the car in 4th gear and it was spot on. With this tune-up, I would back half the **** out of the 1/4 and the 1/8th was no biggie. When I set the tune to better satisfy gears 1-3, I picked up 10mph but lost my back half. If I was ever able to figure out how to satisfy all the gears, I know for a fact I would have been in the 160's, which would have been more reasonable. For the record, this anomaly is something that have seen many times in the manual cars and never see in the autos and I credit that to the load being more evened out throughout the 1/4mi pulls.
Something I've rarely seen mentioned is what all the dyno settings were when someone gets on the dyno. It's something I prefer to know when using a dyno because there's no point in having corrections otherwise. If you're in the general area of what a local weather app reads, I would say you're close enough. All of the above is for comparing notes amongst others. The dyno is really just a great tool for measuring deltas though, something to get you to the track so that you can get it dialed in properly IMO.
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I generally chuckle to myself when guys post their 800 plus dyno numbers then never bring their cars to the track to see what kind of performance they really have. To me having a car that makes big power on the dyno must be backed up by a respectable ET. I'd feel like a real *** if I was advertising my car as a 900 RWHP beast and got dragged by a 700rwhp car.
As an example, stock 2008 LS3 loses 2 degrees of ignition advance if engine temp is 212f instead of 194f. It may well be that hot after several runs...
Was the converter locked or not?
How much slip with your converter? Too much or just ok?
How about timing? Requested vs. actual? Difference between previous runs?
How about AFR? Did you have cat overtemp protection activated or not (independent if you have cats or not)?
Did the engine have exactly same boost in this particular run?
Finally, did you hear the engine knock during pull, even if logs show clean run?
Granted, the car made 860 on nitrous and 820 off it on this tune. The DA didn't change much through the day. So why was my highest trap off the bottle, then my other 9 second passes were 142-144, including other days? It's not like that was my first rodeo. No changes made to the car that day. 149 at 820rwhp with a 6 point, roll bar, a suitcase in the trunk, no drag wheel setup, full street trim. This one I can't figure out. I've discussed this with Alan.
The answer is of course in the logs.
As an example, ignition advance is not static: it depends on multiple things, such as engine cooling temp, iat, burst knock settings (which is not real knock), etc.
Stock LS2 (tune) loses -4 degrees of ignition advance if engine temps are 230f, but of course that does not happen too often. Maybe more in road racing circuits..
When I first dyno'd 1021whp, I got a lot of crap from people in the background saying it was BS. I went to 5 other dyno's throughout the DFW metroplex, dyno'd 1000+ at each site and drove home. When I started track tuning my car, I was able to run 151 in the 1/4, but one very significant thing that I discovered is that gears 1 through 3 were lean. I tune the car in 4th gear and it was spot on. With this tune-up, I would back half the **** out of the 1/4 and the 1/8th was no biggie. When I set the tune to better satisfy gears 1-3, I picked up 10mph but lost my back half. If I was ever able to figure out how to satisfy all the gears, I know for a fact I would have been in the 160's, which would have been more reasonable. For the record, this anomaly is something that have seen many times in the manual cars and never see in the autos and I credit that to the load being more evened out throughout the 1/4mi pulls.
Something I've rarely seen mentioned is what all the dyno settings were when someone gets on the dyno. It's something I prefer to know when using a dyno because there's no point in having corrections otherwise. If you're in the general area of what a local weather app reads, I would say you're close enough. All of the above is for comparing notes amongst others. The dyno is really just a great tool for measuring deltas though, something to get you to the track so that you can get it dialed in properly IMO.
I saw the exact same thing in my C5Z with it being leaner in lower gears. It did it with the stick trans, and the auto trans..
1st = 12.0-12.3 afr
2nd = 11.7-12.0
3rd = 11.3-11.7
4th = 10.8-11.2
Never figured out why..it did it with the auto as well. I just tuned it in 1:1 (3rd/auto, 4th/stick)and whatever it was in the lower gears, it was. I figured you stayed in 1:1 longer then any of the others so....I stuck to that....but I did manage to melt **** too so...
Depends on what you expect the dyno numbers to mean. If you're using them for bench racing, then dyno numbers are all that matter.
In the real world, however, I think they're just a tuning tool.
The dyno says I'm putting 708/605 to the wheels. I think those are accurate numbers, since they're in line with similar builds. And they're backed up by my Butt-O-Meter on the street. Once the track opens, I'll get some track numbers, but I honestly expect those to be very traction limited.
Dynos make tuning safer and are good for before and after results. I dont really care what the end numbers are. I just care how it runs. Most people just want the numbers though.
I can't deny that it's kinda cool having an impressive dyno sheet to show everyone. That's the little kid in me. But the old man in me had rather have the quick ET/high MPH timeslip to show for the efforts instead. I know when we first got the final tune on the Vette last year and it showed 809 RWHP there were people that said the dyno we went to was known for spitting out stupid high numbers. Many said those numbers were not possible with the P1SC-1 supercharger we were running with the meager boost numbers it was able to make. I even questioned the owner of the shop about it. He told me to calm down and we'd talk again after going to the track. Well, after we ran 8.90's @ 154 in and out of the throttle and not going WOT until the 60', I don't think anyone questions this particular dyno's numbers anymore. I guess it's like this: Putting up a big number on the dyno and having a sheet to wave around indicating as such is a cool thing. Having a time slip to more than back up said dyno sheet is the real deal and the ultimate silencer though.
I can't deny that it's kinda cool having an impressive dyno sheet to show everyone. That's the little kid in me. But the old man in me had rather have the quick ET/high MPH timeslip to show for the efforts instead. I know when we first got the final tune on the Vette last year and it showed 809 RWHP there were people that said the dyno we went to was known for spitting out stupid high numbers. Many said those numbers were not possible with the P1SC-1 supercharger we were running with the meager boost numbers it was able to make. I even questioned the owner of the shop about it. He told me to calm down and we'd talk again after going to the track. Well, after we ran 8.90's @ 154 in and out of the throttle and not going WOT until the 60', I don't think anyone questions this particular dyno's numbers anymore. I guess it's like this: Putting up a big number on the dyno and having a sheet to wave around indicating as such is a cool thing. Having a time slip to more than back up said dyno sheet is the real deal and the ultimate silencer though.
Amen..... My next dyno session I'll be looking for 800 plus and if I can run 8.anything in the 1/4, I'll have reached my conservative goal for a streetcar. There are a couple local streetcar events where you have to take a 30 mile drive prior to making passes and I'd like to give it a shot with an 8 sec streetcar.
Amen..... My next dyno session I'll be looking for 800 plus and if I can run 8.anything in the 1/4, I'll have reached my conservative goal for a streetcar. There are a couple local streetcar events where you have to take a 30 mile drive prior to making passes and I'd like to give it a shot with an 8 sec streetcar.
We plan on participating in a few of those this year also. Mostly we're going to do 1/8th mile events though. But doing the cruise in a car that's hopefully going to scare a 4 do death in the 1/8th this year is going to be kinda rewarding.
BTW, we were 3300# raceweight when we ran that if it'll help you in any way setting up your car to run the number we did. Any other details you need and I'll gladly tell you our exact combo if interested. PM me.
04-13-2017, 05:56 PM
Dyno Education - Tips, Tricks, and False Records
seems legit
