Anyone remember some posts I made about my T3 being 'laggy'?

[Tony D]

I would bet the tests in SCC were performed in 4th gear at different rpms. That is generally how you test for boost threshold when you get a new turbo car. It will tell you where you can "get on it" and get full boost with proper response.

So be cruising at say 2500rpm in fourth---level ground, and WOT. Basically throttle is cracked open so the AFM is already opened slightly. You will find the response lag from the EFI goes away above about 32/3500rpm as that is about where the AFM flap is pinned up against the "full open" stop internally.

Then do it again at 3000, and again at 3500, etc etc etc...

 

Then go from 7 to 10, and see what you get.

Then go from 10 to 12, repeat.

Then go from 12 to 14. If you it from 2000rpms and chart it out, you will find some corves that might be useful in determining how the turbo responds.

[Guest bastaad525]

errrmmm well I'll probably only try at stock boost and 14psi... while adjusting the grainger ball valve is easy as can be, fine tuning it and pinpointing any particular amount of boost can be a pain in kiester (keister?).

 

Also, I know the boost threshhold has been moved up a bit after the I/C install. Before the I/C I could easily get full boost at around 2800rpm or so if I remember right? Now it's maybe 500 rpm hire. I consider 3500 to be the threshhold for all intents and purposes, and if I need to go in a hurry if I'm not already above 3500rpm then I'll usually downshift.

 

But I'll try at different rpm of course just to see... so I'll bring it to the rpm and hold it, cruise steady and then WOT. Oh and in 4th gear if I CAN... I dont remember for sure but I think 3500rpm in 4th gear is probably breaking any speed limit that's posted locally...

[Guest bastaad525]

hey I just got a PM from big-phil on these boards who has been posting a bit lately having just completed his turbo swap.

 

he tested his own setup, T3 set to hit 14-15psi, doing exactly as I asked with holding the rpm and then flooring it and counting how long his turbo takes to spool.

 

His is taking about exactly as long as mine is... I'll quote him here:

 

"In 3rd gear at 3500rpm I punch it and say "one-onethousand two" by the time I say "two" its at 14 pounds. I did it two or three times and it was the same each time"

 

I used to test this way with just one one thousand two before I got ahold of a stopwatch and yeah that's exactly what mine would do. I know the old one one thousand isn't exact but unless he's counting overly quick it's taking his T3 one full second or more to hit 14psi just as it is with mine.

 

I'm still hoping I can get some other guys to test this and hopefully with a stopwatch but the more I dig the more it seems that my 'slow' turbo is actually quite normal...

 

Havent gotten to drive the car recently so still haven't been able to test as Tony suggested but I will

[Guest bastaad525]

I would bet the tests in SCC were performed in 4th gear at different rpms. That is generally how you test for boost threshold when you get a new turbo car. It will tell you where you can "get on it" and get full boost with proper response.

So be cruising at say 2500rpm in fourth---level ground' date=' and WOT. Basically throttle is cracked open so the AFM is already opened slightly. You will find the response lag from the EFI goes away above about 32/3500rpm as that is about where the AFM flap is pinned up against the "full open" stop internally.

Then do it again at 3000, and again at 3500, etc etc etc...

 

Then go from 7 to 10, and see what you get.

Then go from 10 to 12, repeat.

Then go from 12 to 14. If you it from 2000rpms and chart it out, you will find some corves that might be useful in determining how the turbo responds.[/quote']

 

Tony (and everyone) I redid the tests as per your prescription, holding the throttle to maintain a steady rpm (at about 15 inches of vacuum), then floor it. I didn't try 2500rpm, but I did try 3000 and 3500 rpm and got identical results. From the instant I floor it, I get to 14-15psi in about 1.2 seconds (the average after several tests).

 

I removed the boost controller and tried it on the stock 6psi (used to be 7 before the I/C... pressure drop) and found it took an average of .6 seconds to get there under the same testing conditions.

 

As I mentioned before... tweaking the grainger MBC is kinda a hassle so I didn't bother with trying at the various boost levels.

 

So yeah... definatley faster if I do the test that was as opposed to being completely off the throttle and then mashing it, which added about .3 seconds.

 

oh by the way this testing was done on the street so I had to do it in 3rd gear... didnt' want to go THAT fast, and didn't really have the chance to hit the freeway and try it in 4th but I dont' imagine it would boost that much faster? Maybe a couple tenths if at all, so let's just call it one full second to boost full 14 psi.

[thehelix112]

Just got my car back to a drivable state (-3.5 deg front camber for me!) so I'll go tomorrow and see what I get.

 

Dave

[Guest bastaad525]

sweet thanks! looking forward to it and use a stopwatch if you can!

[thehelix112]

Using computer. More accurate.

 

Dave

[Guest bastaad525]

cool and the more detail you can give the better please!

[thehelix112]

2.28 seconds from 3000rpm to 15psi.

 

Not too surprising really, it is just an eensy bit bigger than a stock T3.

 

Dave

[Guest bastaad525]

thanks dude well there you have it

 

unfortunately my car is already long gone... but your results do fall right in line with what I was experiencing on my stock T3. I think people who say that the stocker spools 'instantly' are just optimistic or not very picky at all

 

well I've given rides to a lot of people and even a few people have driven my car, also the guy who bought it... and none of them have ever said the car felt at all laggy. It only felt laggy to me after I bought an SRT-4 which has one of the tiniest turbos any of us have probably ever seen and even that doesn't spool 'instantly'. But it spools very fast and by comparison the Z felt like it did have a lot of lag. Jumping from one car to another certainly does have a way of changing your perception on things.

 

In the end I feel better though because now I'm pretty sure there was actually nothing wrong with my car or turbo... even though the car is gone it's good to know it was behaving more or less normally, as I had been convinced by all these claims of the T3 being 'lag free' that I must have either done something wrong or had something wrong with my turbo.

[thehelix112]

All good.

 

Dave

[zeiss150]

well .... I don't know $hit about $hit, but... in Corky bells book he say's there no such thing as a turbo with no lag. If you want a turbo with no lag ... build an LS2 :burnout:just my dumb 2 cents.

 

BTW ... I'm building a turbo L28 ... great info!

[Guest bastaad525]

well .... I don't know $hit about $hit' date=' but... in Corky bells book he say's there no such thing as a turbo with no lag. If you want a turbo with no lag ... build an LS2 :burnout:just my dumb 2 cents.

 

BTW ... I'm building a turbo L28 ... great info![/quote']

 

agreed... as I said, even the extremely small turbo on the SRT-4 has a measurable amount of lag, close to a full second.

 

For me it just seems like it was 'one of those things'... like when people say stuff like a car handles "like it's on rails", or "stops on a dime". Now it's "T3's have no lag" :mrgreen: Shoulda just took that with a grain of salt instead of spending time trying to figure out what was 'wrong' with my car!