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

[Guest bastaad525]

In this thread here:

 

http://forums.hybridz.org/showthread.php?t=106249&highlight=lag

 

In it I had stated that, at 3000 rpm, with my foot completely off the gas, if I suddenly floored the gas it took roughly 1.5 full seconds to hit full boost (14psi). I got a bunch of replies saying that something must be wrong with my turbo or something else, that this was WAY slow for a stock T3 to spool.

 

I've been going thru some old articles in Sport Compact Car, and found an article where they were covering their Project Silvia (240SX SR20DET conversion). For anyone who doesn't know, this car has the Garrett "Disco Potato" turbo, which is a small turbo (smaller than the T3), I think the designation is GT28RS, it's also a ball bearing turbo if I'm not mistaken, so supposed to be quicker spooling. I mean, I would think it spooled MUCH faster than a stock T3 and at a lower rpm... but then I read this:

 

"Mashing the throttle at 2500 rpm in second gear in cool evening weather, the Disco Potato takes a little less than three seconds to reach full boost. The bleed valve spikes to 17 psi before settling to the boost target, while the Power Enterprise controller has no overshoot and actually helps the turbo spool very slightly faster."

 

a small, ball bearing turbo... three full seconds to spool even with an electronic boost controller!!!! I know the RPM was sorta low... but such a small turbo and ball bearing at that I would think it'd have no trouble spooling up quickly even at that rpm. It's hard to guess how much difference 500rpm would have made.

 

I know my car spools up at about the same speed at 2500rpm as it does at 3000, which is, as I said, takes about 1.5 seconds to hit 14psi, actually timed with a stopwatch. My SRT-4, with a very VERY small Mitsubishi TD04, does it in just under a second, like 3/4 second actually.

 

 

So I dunno... I feel a little better. A couple of you guys had me feeling like my Z must have some serious kind of problem to be spooling so slow, but after reading this it seems maybe it's not so bad after all?

 

What do you guys think?

 

 

EDIT: ROFL I should have read a bit further on before posting... ah well here's some more info. Turns out they tested the same car and boost controller from 4000rpm as well. Here's the result quoted:

 

"Mash the throttle at 4000 rpm under the same conditions and full boost takes only a second."

 

There's a graph there and actually it's a hair over a second, like 1.2 seconds.

 

So what the heck were you guys talking about something wrong with my T3?? If I can get full boost at 1.5 seconds at 3000rpm, I can probably get it a little faster at 4000rpm with the increased load and whatnot... and here they're running a small ball bearing turbo and getting full boost in just over a second as well... doesn't seem like there's anything wrong with my T3!! And you guys who claimed yours boost full 'instantly' or way faster than what I was saying... either have freak turbos or don't know how to count

[Thumper]

One thing you need to remember is they are using the disco turbo on a 4 cyl with 4-valves per cyl designed for high rpm. And z is a inline 6 designed for low rpm power. So you can't really compare rpm to rpm. What you can compare is time it takes to spool at the torque peak of both motors. Roughly 3k for the Z and 4k-4.5k for the 4 cyl.

[GrayZee]

Yeah, I second that.. a different engine is a different engine, can't really compare apples to oranges.

[Guest bastaad525]

I had considered that as well. I know the 2.0 L isn't moving as much air as the L28 so that would factor into a slower spool. The point is, to hear these guys rave about this turbo, it's like it was the quickest spooling thing, which was a huge factor in why they picked it. To hear (SCC writer) Dave Coleman talk about that turbo, it's like "it's so lag-free it's more akin to driving with a larger displacement engine than a turbocharged one".

 

But when I talked about how long it takes my turbo to spool, guys were saying it was way too slow and something had to be wrong with it... then come to find out this super-lag-free turbo on that Silvia spools only a few tenths of a second faster than my ([sarcasm]obviously defective[/sarcasm]) T3.

 

So... my turbo, floored at 3000rpm (torque peak) spools 14psi in 1.5 seconds, their smaller BB turbo on a smaller engine, floored at 4000rpm (torque peak) does it in 1.2 seconds.... still making me feel better and not so much like my turbo is defective

 

 

But, you still make a good point... it's still kinda comparing apples to oranges. But for everyone who was saying something must be wrong with my turbo for it to spool so 'slow', I'm still waiting for anyone to take a minute of their time and do as I did and actually sit there and time how long it takes to spool instead of 'oh it spools near instant'. So if anyone wants to help me out there, especially if you have a similiar setup to mine, go out and try, from different rpm points (I do all my testing in 3rd gear, and try from 2500, 3000, 3500, and 4000rpm), let completely off the gas then punch it and time how long it takes your turbo to spool. It would also help the comparison if you're running similiar boost to me, currently 14psi (with a very brief spike to 15-16psi). It would help me to see if maybe there IS something really wrong with my setup or if this 'slow spool' is actually normal.

[260DET]

Have used both a high flow TO3 and a GT28RS on my two liter engine, there is no comparison. About 50 more hp at the wheels for a total of 270 whp using limited boost with the RS plus a much superior response that actually is like driving a NA V8.

 

A TO3 should spool quickly on a L6, it is relatively small for a engine of that displacement with the consequence that maximum output will not be high. And comparing two different turbos on two different engines is meaningless.

 

I'm being abrupt on this subject because there seems to be a school of thought around that in effect rubbishes the big step forward gained by aerodynamically superior BB turbos. Which can be misleading to those who are trying to learn something about what type of turbo they should use.

 

You can see the two liter engine in my gallery, link below.

[Guest bastaad525]

which is all fine and well but still leaves me with my main question... if my stock T3 is taking ~1.5 seconds to spool to 14psi at 3000 rpm, is that slow, indicating a problem, or is that normal?

 

I already said, I understand that a GT28RS on a 2.0 L and a T3 on a 2.8 is comparing apples to oranges, but subjectively, the GT28RS is described as a super responsive turbo with next-to-no lag, yet when tested on the 2.0L SR20 it took 1.2 seconds to spool to 15psi at 4000rpm. So... a turbo being described as super responsive and lag free takes 1.2 seconds to reach full boost, yet if my T3 takes ~.3 seconds longer, there is something wrong for it to be spooling so slow? While from a technical aspect it's comparing apples to oranges, subjectivity is... well... subjective So... how can 1.2 seconds be 'super responsive and lag free' on one car, but 1.5 seconds is 'something must be wrong' on another?

[Phyxius]

sounds like a boost leak or a stuck open wastegate to me... My t3/t4 hybrid spools to 15psi in about a second from 3k rpm. Sometimes my charge pipes will get loose and it will start taking longer to spool.

[Guest bastaad525]

there might be a boost leak... that's one thing I haven't been able to check as I haven't gone and made a tester yet (I need to do this... SRT-4's are notorious for coming from the factory with ill-fitted I/C hoses causing boost leaks). I did recently go thru with a socket wrench and really crank down on all my hose clamps... until now I've only ever tightened them with a screwdriver. It didn't make a difference. I wonder if my I/C itself might be leaking? Or maybe my intake manifold gasket or TB gasket...

 

By the way, a T3/04 spooling to 15psi in a second is pretty damn fast... I really really wish one of you guys would time it with a stopwatch... hell, the tiny joke of a turbo on my 2.4L SRT-4 takes a hair less than a full second, about 3/4 of a second to be exact, at 3000 rpm or more. And a T3/04 absolutely DWARFS that turbo. I can't emphasize just how small that turbo really is... put it this way, there is more of a difference in size between the stock SRT-4's turbo and my stock T3, than there is between a stock T3 and a T3/04. The SRT turbo is TIIIIINY.

[thehelix112]

I will be timing mine (with the computer's data logger) the next time I drive it.

 

Dave

[Phyxius]

Have you blocked off the pop off valve? I'd assume that you have. There are many things attached to the manifold that if not operating correctly could cause a leak.

[wigenOut-S30]

I did this tonight.. My stock T3 turbo from no throttle to WOT at 3k rpms took me alittle under a second to hit 10psi. I dont understand why you are testing it at no throttle though? when cruising at 3k rpms and punch it it is way less then a second to reach 10psi. this is with stock ECU stock injectors 200+k turbo motor and 2.5 crushbent exhaust.

[Guest bastaad525]

well to be specific, what I do is accelerate up to 300-500rpm higher than the exact rpm I want to test from... so, if I want to test at 3000rpm, I'll acclerate (easy, not WOT) up to ~3300rpm, then let off the gas completely. RPM drops slowly, and as soon as the needle hits 3000rpm I punch it and start my stopwatch.

 

Of course, if I'm actually steady cruising at 3000rpm (somewhere in the 10-15% throttle range I'm guessing) and then punch it, it will spool up a tad bit faster.

 

It just seems to be a more exact way to test, doing it that way.

 

I really... REALLY wish I had timed it before adding the I/C... because I swear it spooled way faster before the I/C, I do know I was hitting full boost (10psi at the time) at a lower rpm, like 2400rpm, whereas now I get full boost at more like 2800rpm. I imagine it could have increased spool time by as much as half a second. I've been tempted to get another stock J-pipe and run w/o the I/C and time it to 10psi. I know if I pull off my boost controller and run the stock 6psi (some pressure drop across my I/C) on the stock WGA, I get full boost and NO spike in less than a full second.

 

About the pop off valve and other stuff like that, I'm running the N42 intake from an early 280z, so there's no EGR, pop off or 90% of the other stuff that is on a stock turbo manifold. I even had the PCV hole on the bottom of the manifold and some nozzle on the top (I dunno what it was for) welded shut. So if there's a leak, it would be either a) the I/C itself, the gasket between throttle body and manifold, or c) the manifold gasket. There may be other little places that I"m not thinking of (the reference line for my boost gauge comes to mind) but that's about it.

[thehelix112]

525,

 

what gear did you do your tests in again?

 

Dave

[Guest bastaad525]

usually 3rd gear, sometimes 4th as well but I forget now if 4th made any difference in the time it took to spool.

[karay240]

Another thing to consider about the different turbos is not only how quick they spool, but also the way in which they spool. The traditional journal type will spool later more abruptly, while the BB turbo will be more linear boost curve.

 

This is what contributes to the "instantaneous" throttle response of the BB turbos.

 

When I say instantaneous, I mean this as a relative term. Just about anytime you put a larger turbo on a car it will spool later.

 

Just as a side note, though, there is nothing really wrong w/ the jounal type. The newer turbos can run tighter clearances than the BB turbos, and have been getting better throttle response as well as top-end.

[thehelix112]

karay240,

 

I've heard exactly the opposte re journal vs bb. From what I understand the BB has lower rolling resistance which means the wheel accellerates faster and boost comes on much faster.

 

Dave

[beren]

Another thing to consider about the different turbos is not only how quick they spool' date=' but also the way in which they spool. The traditional journal type will spool later more abruptly, while the BB turbo will be more linear boost curve.

 

This is what contributes to the "instantaneous" throttle response of the BB turbos.[/quote']

 

I've heard exactly the opposte re journal vs bb. From what I understand the BB has lower rolling resistance which means the wheel accellerates faster and boost comes on much faster.

 

thehelix112, I think karay240 means that BB turbos spool like this:

|               .
|             .
|           .
|         .
|       .
|     .
|   .
| .
-----------------

 

and the journal types spool like this:

 

|               .
|              .
|             .
|            .
|          .
|        .
|     .
| .
-----------------

 

The flatter curve at the beginning and the sharper curve at the end would contribute to a journal turbo having the perception of a longer lag with more of a punch at the end. A BB turbo, starts spooling easier, so it doesn't have the sharp spike at the end, it just works its way up to speed smoothly.

 

You guys were agreeing with each other.

[Guest bastaad525]

I will be timing mine (with the computer's data logger) the next time I drive it.

 

Dave

 

helix did you ever time yours? what did you find?

[Tony D]

well to be specific' date=' what I do is accelerate up to 300-500rpm higher than the exact rpm I want to test from... so, if I want to test at 3000rpm, I'll acclerate (easy, not WOT) up to ~3300rpm, then let off the gas completely. RPM drops slowly, and as soon as the needle hits 3000rpm I punch it and start my stopwatch.

 

Of course, if I'm actually steady cruising at 3000rpm (somewhere in the 10-15% throttle range I'm guessing) and then punch it, it will spool up a tad bit faster.

 

It just seems to be a more exact way to test, doing it that way.

[/quote']

Nope, you are exacerbating the problem of on-boost response by starting from full drop-throttle. Almost a full second (up to .750 of a second) will be the inherent lag of the stock AFM system moving the flap open, then recalculating the WOT position, then moving to the fuel fuel map. Even an N/A engine with the stock AFM system will have a noticable delay when you do the test in that manner. I can feel it in every N/A Bosch system I have ever driven, and it drove me to distraction especially in the Z. Floor it, think about it, then GO!

 

From GO! your turbo then spools up.

 

It's a function of an inappropriate testing procedure, combined with electronic lag. I noticed when using L28ET electronics the boost response was MARKEDLY SLOWER than when I had my Mikuini Triple Blowthrough setup on the car, and the Mikuini's had response akin to the Megasquirt when they were running well.

 

The Megasquirt boosts FAR faster than the stock system.

 

It's not the turbo, a lot of it is in the electronics you are running. There is not enough advance to heat the exhaust, fuel shot to make heat and exhaust velocity...etc etc etc.

 

In short, even SCC did not run their cars closed throttle to WOT. And remember anything below boost threshold is not lag, it's improper driving.

 

Having been in JeffP's car recently, I can attest to the fact that at 2800rpms I can't even get "One" out of my mouth after he says "NOW" and floors it, before his setup is at 8psi. At 2800rpms on a big turbo, with Z31 Electrics...

 

I can't wait to see what it does at 15psi, and where that boost threshold rpm will be...

[Guest bastaad525]

Okay Tony D... that makes sense and yeah the throttle response on the EFI sucks... when I had my 2.9L N/A with SU's it was just INSTANT, but yeah this car and the other two 280zx's I had with stock EFI there's always been that delay... I dont know if I'd say 3/4 of a second but it is a definately delay almost a bog.

 

Okay so what would be the best way to test it? Give me a really specific procedure including how much throttle and at what RPM and I'll go back out with the stopwatch and measure it again.

 

For the heck of it I might take the MBC out and try it again just on the stock 7psi and see how fast it spools that way. I am 90% sure it takes less then or right on a full second to hit 7psi, and then yeah maybe an extra half to get the additional 7 to 14.

 

But I do like your reasoning and explanation on it and again I feel a bit better about the whole thing... I never even considered the delay from the AFM as being part of the problem.

 

So prescribe me a 'proper' method for doing this test and hopefully I'll come back with some better numbers.