Carl Heideman
Carl Heideman
10/26/20 10:58 a.m.

Modern technology is changing how we interact with classic cars, and sometimes we can’t help but laugh. After all, these situations can get pretty anachronistic.

More and more, we rely on high-tech tools to keep our classics in tune. Static timing has been replaced by dynamic timing; reading spark plugs has been replaced by tailpipe sniffers; and the holy grail …

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240zdave
240zdave None
6/3/21 10:32 a.m.

That's John Williams doing a dyno run at Balanced Performance in Sugar Hill, GA.  John built the engine and transmission for my race car, and tuned it on that dyno.  I miss John a lot, especially when I'm at the track.

Maple6
Maple6
9/4/22 12:39 p.m.

Totally agree about the value of the dyno.  I'm interested in comparing chassis dyno numbers with flywheel numbers. Several years ago I organized a dyno day where we had 5 TR6s & a TR250 on a chassis dyno. Two of the 6s were stock except aluminum flywheel on both with fresh engine rebuilds.  The hp numbers for these two cars were within a couple of hp. Using a rule of thumb of 25% loss at the rear wheels, the bhp numbers were right at the Triumph factory claim 105.  Does anyone out there have any hard data Ora formula for computing bhp from dyno hp?

David S. Wallens
David S. Wallens Editorial Director
9/22/22 9:27 a.m.
240zdave said:

That's John Williams doing a dyno run at Balanced Performance in Sugar Hill, GA.  John built the engine and transmission for my race car, and tuned it on that dyno.  I miss John a lot, especially when I'm at the track.

Yes, John was good people and miss him as well. I met John when working at Automod, so 1992-'94. He was a customer. My first race tires were his take-offs. They didn't quite fit, but I was able to trade them for a set that did. 

rsporter
rsporter
12/5/22 12:10 p.m.
Maple6 said:

Totally agree about the value of the dyno.  I'm interested in comparing chassis dyno numbers with flywheel numbers. Several years ago I organized a dyno day where we had 5 TR6s & a TR250 on a chassis dyno. Two of the 6s were stock except aluminum flywheel on both with fresh engine rebuilds.  The hp numbers for these two cars were within a couple of hp. Using a rule of thumb of 25% loss at the rear wheels, the bhp numbers were right at the Triumph factory claim 105.  Does anyone out there have any hard data Ora formula for computing bhp from dyno hp?

You won't find any hard data, as each vehicle can be different. But, for near 30 years now (since Dynojets started becoming common), we've gone with a 15% loss (from crank to wheel hp) for RWD manual trans, 18% for FWD manual trans. Add 3-4% for the auto trans versions. Lately, though, some of the newer auto trans, and especially the DCTs, are down around the MT loss percentages.

Using a lower percentage loss is more realistic, as higher loss #s inflate the theoretical crank hp number

 

 

frenchyd
frenchyd GRM+ Memberand MegaDork
12/6/22 8:05 a.m.

Classic and Vintage cars really need to  go on the dyno.  
 Fuels are different now from when the cars were built  ( they no longer have lead in the gasoline but typically will have alcohol). In addition engines typically  are  oversized in the rebuilding process.  
 Thus fuel requirements, even timing will be different.   To be able to properly test and adjust to needs helps ensure safe, reliable usage. 
  A typical dyno pull is no harder on the engine than climbing a steep hill.   If the engine blows up on the dyno it would have blown up shortly after installation anyway.  

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