spoolup time

Blazer406

Mechanical Engineer
Joined
May 2, 2002
What time (in seconds) is "normal" for a decent spooling setup.... from hit of the gas....on the transbrake....to say 5-8 psi boost.... on a 74GTQ on a 234" motor?

Inquireing minds want to know.

Also... what can you do in your tuneup to make it spoolup faster? timing? target AFR? EGT's?
 
I doubt you'll get anyone to tell their secrets. Not all cars like the same things.. mostly trial and error. Differences in cams, heads, etc.
 
Back when my car was together, stock 109 longblock with GT67 ptrim plain bearing turbo, atr headers, v2 fmic, and yank 2800ish stall converter, stomping the gas from a dead idle while logging with direct scan, the time from the first frame where the tps changed to the first frame with the maf over 175 (could have been 230; it's been several years, it was about 5 psi and at least 2 psi before the tires would blow away) was down to about 1.6-1.7 seconds after lots of tuning. I'd have to dig out my notebook to be sure but I think that was before I put in the lm1 and started logging map. On a friends car with a plain bearing 76 ptrim and 3000 or 3200 stall converter we got his down to 1.8-1.9 seconds after an afternoon of tuning. He didn't tell me he had put on the bigger turbo, he just said the spool was a little lazy and he hoped I could improve the chip a little (he was running one of my street chips). He didn't fess up about the turbo change until he had some time slips at the track :). A well known tuner actually called him a liar at a track rental because he didn't believe that turbo could spool like that so he insisted my friend still had his 70 on the car. Basically just optimizing the fueling and a couple of very small tweaks in the stock timing table. I started with my car with red stripes way way back, and basically used the couple of timing changes Tom Chou made in the stock table for his Thrasher chips. Then I used that base to make a chip for 50's and a chip for 72's and in each case I just worked the fuel curve until the spoolup and wot fueling was good. No magic, just systematic testing and note taking using that time-to-a-maf-value to track progress quantitatively.
 
Thanks Carl.

I think this one currently w/o any attention to spoolup (yet)... is around 2 seconds or so..... obviously it spools up from there very quick......

I haven't messed with it yet.... but I would think.... hotter EGT's during spoolup would be a good thing to a point...... and decently high timing..... but that is a guess on my part....

IMHO... a journal bearing 74GTQ with a 85 housing....on a 0.030 over 231.... is bound to spool slow to an extent.....should like a lot of converter.......
 
I doubt you'll get anyone to tell their secrets. Not all cars like the same things.. mostly trial and error. Differences in cams, heads, etc.

I wasn't trying to get everyones secrets..... just a little reality check on what to expect with a turbo of this size on a motor of this size.

I'm sure the TSM boys have a 71GTQ spoolup down to under 1 second on a well tuned stroker motor.
 
Timing...................................but like Jason said earlier, every engine reacts differently due to many variables.
 
All depends on the converter and turbo housing size. Alot of guys don't care for it becasue they pre spool the car at the line. However on the street its a different story. With your setup it already sounds like you need a BB turbo......
 
All depends on the converter and turbo housing size. Alot of guys don't care for it becasue they pre spool the car at the line. However on the street its a different story. With your setup it already sounds like you need a BB turbo......

Not my setup... it is a friends.... we are just tuning a little.... wanted to know what is reasonable.....

He does have a larger bb turbo, but it has to go in for a rebuild....so it is out of commission until then. The 74GTQ is a backup...IMHO it runs real good with the 74..... but I think I might can tune it a little different during spoolup to get a little better response.....
 
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