spoolup time

[Blazer406]

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?

 

[V6RACER]

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.

 

[ijames]

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.

 

[Blazer406]

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.......

 

[Blazer406]

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.

 

[V6RACER]

I'm sure the TSM boys have a 71GTQ spoolup down to under 1 second on a well tuned stroker motor.

 

[Blazer406]

crickets..........

 

[Bent6]

Timing...................................but like Jason said earlier, every engine reacts differently due to many variables.

 

[norbs]

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......

 

[Blazer406]

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.....