How do you dyno an auto?
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On The Tree
Joined: Jul 2010
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How do you dyno an auto? I just recently had my car dyno'd, its an 1996 a4. I thought I would have to some how lock the converter for the dyno run but the guy that owned the dyno said that id have to start my dyno run at 3500rpm in 3rd gear to avoid flashing the converter. Ive never dyno'd an auto before so i went ahead with the run.
I do plan on getting a 3600 converter soon and doing another dyno run after i install some 1.6 rrs. I don't want to have to start my next dyno run at 4000 rpm to avoid flashing the 3600 converter. How is everyone else dynoing there automatic LT1's? Thanks.
I do plan on getting a 3600 converter soon and doing another dyno run after i install some 1.6 rrs. I don't want to have to start my next dyno run at 4000 rpm to avoid flashing the 3600 converter. How is everyone else dynoing there automatic LT1's? Thanks.
Teching In
Joined: Mar 2007
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From: Clermont FL
When I had my car dynoed the guy could not get it right. He ended up doing it in 2nd gear and could only pull to 4500 for some reason, needless to say my #'s were kinda low due to this, good thing it was free or I would have been pissed. I dont know what the trick is.
Thread Starter
On The Tree
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That sucks, but there has to be somthing we can do to lock the converter. I would rather have started my run at 1500-2000rpm vs. the 3500rpm that i ended up doing. At 3500 im already cutting into my power band. My numbers were good though, I had an average of 291hp and 316tq
On The Tree
Joined: Dec 2011
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From: Kissimmee, Florida
My buddy has the same problem with his Pewter 02 SS convert. He had a 4000 Yank converter and dynoed nothing on the first run, after they revved/work'd the crap out of it. They did something with their dyno (where the roller was, but underneath) and made another attempt. He did a low 382whp, whereas he normally hits between 438-446. I am curious as to exactly what they do though...
TECH Regular
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Its a good question! How would they do it with a Turbo 400? Seems until you at least get to your stall speed there would be no accurate numbers and even then, I am sure there has to be "Some" amount of slippage no matter what.
Joe
Joe
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On The Tree
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Thread Starter
On The Tree
Joined: Jul 2010
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Thanks! I had an M6 LT1 a few years back with the same mods except no tune that dyno'd 302hp so being as close to that as I was being an auto made me happy. I was with a group at the time of my current dyno and I told them id be happy with 275-285hp. My lowest pull was 288hp and my highest was 295hp. I think if i get 1.6rrs and retune it again ill get over 300hp. I just want to figure out how to lock my converter so i can get a full run on the dyno.
When I had my Monte with a TH400 dyno'd they just put it in 3rd gear and nailed it. Converter is a 3000 stall that flashed to about 4700. I was kind of disappointed when the #'s seemed kind of low but after a trip to the track I know they're low lol. Either that or my car somehow lost about 500 lbs without me knowing!
TECH Regular
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When I had my Monte with a TH400 dyno'd they just put it in 3rd gear and nailed it. Converter is a 3000 stall that flashed to about 4700. I was kind of disappointed when the #'s seemed kind of low but after a trip to the track I know they're low lol. Either that or my car somehow lost about 500 lbs without me knowing!
I have a close friend in the Motocross Aftermarket business. One day I was at his shop when he was dynoing pipes for the Kawasaki V-Twin quad. No matter what he did the power numbers kept reading plus or minus one HP and he was getting pissed off and kept saying there is NO WAY something is wrong with the dyno! I told him, "Look at your Times to RPM and that is where you will see the results!" With the Variable belt tranny, the tranny absorbs the HP/Torque with increases in RPM. When he did that he said, HOLY CRAP! He had wasted a day chasing HP/Torque numbers and never looked at the Time/RPM and that is what you need to do with that system, lol! Would have been a week if I hadnt stopped by, lol!
Joe
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From: centerville, ohio
Third gear happens to be the 1:1 ratio required to make an accurrate dyno run. To make the run through a locked or unlocked converter is a matter of preference, but like already said has to be modified via the tune. I run a 1993 engine and trans and have hit the dyno 5 times over the years. Regardless what stall you have, you must maintain a certain wheel speed to prevent kick down into second gear. For me it happens to be 65 mph which starts the run around 3300 rpm. Anything below that does't matter since my peak torque is around 4400 rpm anyway.
Unless you have a converter that is designed to be locked at WOT you don't want to lock it on the dyno and roast the lock up clutch. Its not worth it for the 5-10hp you're gonna get. The key is what lt1-xjs said is keeping the speed high enough that it doesn't down shift. If you have tuning software you can modify the tune to keep it from downshifting if you want to start the pull lower.
Third gear happens to be the 1:1 ratio required to make an accurrate dyno run. To make the run through a locked or unlocked converter is a matter of preference, but like already said has to be modified via the tune. I run a 1993 engine and trans and have hit the dyno 5 times over the years. Regardless what stall you have, you must maintain a certain wheel speed to prevent kick down into second gear. For me it happens to be 65 mph which starts the run around 3300 rpm. Anything below that does't matter since my peak torque is around 4400 rpm anyway.
Like he said, locked vs unlocked is a matter of preference; there is no "standard". Starting the run at a given rpm or mph is generally to avoid the 2nd gear kickdown, and that happens to be 3000 rpm or greater for stock shift tables.
Of course, you can program the table ahead of time to have it remain in 3rd gear no matter where you start the pull. in that case, I'd program the TCC locked also to give meaningfull tq/hp numbers at the low revs.
FWIW, some mid-stall street converters are so efficient that you'll barely see a difference locked vs unlocked (other than the higher torque values down low with unlocked). With Yank 3000 and Vigilante 3000 converters in two of my vehicles, the dyno showed less than 2 hp difference locked vs unlocked. With an Edge 3400, it showed 15 hp difference.
