spool up

[buddiiee]

i heard that the stock exhaust manifolds are actually pretty good. is this true? the owner that had my car before me, threw some crap steel headers on there, and my mechanic says that due to your crappy headers, and really wierd crossover, your spool up is severly hampered. how much is my spool up hampered? what else affects spool up. ive nothing to compare my car to, so ive no clue if my cars spool up is slow or not but, i sorta do think its slow,, when i mash the gas, it reall does just sit around for a while. when it spools its fast, but, it takes soo long. my overall throttle response is actually really slow. besides new injectors, which i hear are alot more responsive, what else can i do to decrease my turbo spool time...

[Keller]

Stock headers, with some mild clean-up work, are good well into the 10s.

There is no way to tell "how much" what you have affects anything; good or bad.

Injectors won't help spool. A higher stall converter might, but its the wrong fix for a set of headers if they are the cause. Don't fix a problem with another problem.

Its all about combination. If you have a larger turbo, sometimes you need a higher stall converter, matched to the turbo. As well as increased injector sizing to match the airflow of the turbo. Proper chip programming (i.e. timing and fueling adjustments) help, too.

[buddiiee]

oh no i know that, injectors have nothing to do with spool up, i meant that as in helpin out my overall throttle response thats all.
so, in your opinion, everything else bein stock, (cept my k and air filter) if i throw on this new 2.5" atr stainless dual system, on my reworked stock exhaust manifolds, with that 3" stainless downpipe, all i would need to do, is get a chip that helps me out in the fuel and timing side of the house, and id have a quicker turbo response ya think? any help would be greatly appreciated. thanx

[kenmosher]

As you free up restricition on the exhaust side, spool will be improved. The chip can also help spool with some of the "quick spool" tricks in them.

[buddiiee]

outstanding, thats good stuff. i was also reading, that turbo comparison on here, talkin about different sizes, appearances, cfm rates etc etc. was interested me was the different types of bearings on those things. ones fluid, ones ball bearings. they said the BB ones are quicker, and easier to spool BUT, since their turbine wheels or impellers, or whatevertheheck theyre called, are bigger (im gonna upgrade here shortly) isnt that more rotational mass now? so now that the thing spins easier, but is heavier, am i back to square one all over again? also, i seen that the impeller on the gnx's is ceramic for better head dissapation, and its lighter, to improve spooling, do these new 'high speed' turbos do the same? are there even better improvements out now? what about a titanium impeller? light and heat resistant. anybody do that now? can you recommend a few chips, that are able to be cut, with that little 'quick spool' trick in em? thanx a lot.

[kenmosher]

As far as back to square one ... yep, kind of ... the reason for the BB center sections was to allow for bigger wheels with less lag than without ball bearings.

The ceramic turbos in the GNX were on the exotic side of the spectrum and were vulnerable to breaking if any foreign debris went thru the exhaust (they even had a sediment trap to try to catch things). Needless to say they are really expensive (and rare).

"Normal" turbos have continued to be improved over the years with new wheel designs, different thrust bearings, and even new turbine housing castings. All using more conventional materials and assembly techniques. The key to turbo selection is understanding the compressor map and then keeping it in the "sweet" spot for maximum efficiency ... this might involve a higher stall converter, less/more cam, bigger/smaller tires, etc. Big turbos are going to need more RPM/exhaust energy to spool and to keep in the sweet spot ... just the nature of the beast.

Lots of neat tricks have been done to improve the spool up ("boost spool" strategies in chips, new housing designs, new wheel designs, new bearings, etc.) but physics steps in at some point and it becomes a game of diminishing returns. The application then has to match the turbo (head flow, converter stall, etc.).

[buddiiee]

so how are these tr's with the huge turbos turnin in 11 second times? are their whole engines rebuilt then? so should i not go higher than a ta49 then? all i know is, this 2000 audi a6 2.7t twin turbo whooped me like i put it in reverse. he pulled away so fast from a 30 roll i couldnt believe it. found out there is 2 super small turbos on there, which im assuming have super duper quick spool cuz theyre soo small. would it be possible, if i were to throw on all the standards, (2.5 exhaust, nice injectors, good cold air kit, nice intercooler) to go with the smallest turbo out above my stock one and still run mid 12's? what do ya think. for what i do, a super quick spool up is absolutely essential. if i can get the jump off the line, i can keep em and hold em the rest of the way. its just that i can never get the jump. whaddya think.

[kenmosher]

It's really not that difficult ... TA49 is good down to the mid 11s with a good combination. I ran 11.50s on a TA49 with the stock intercooler and 009s (ported heads restalled D5 converter, and very mild cam).

The 60/61/62 turbos are larger turbos, but with a little bit of converter, intercooler, and enough fuel ... low 11s/high 10s are possible without anything outrageous in the combo.

Then you step up into some of the Te45/45a/63 type three bolts and you start seeing some more aggressive converters and more engine work (usually girdles and such) to handle the power.

Then you get into the various 72/74/76/8x turbos which are in the "serious" category (like TSM ... 9s and 10s).

STOCK turbo will turn mid 12s all day long (with octane to support 21 psi or so of boost). My car, full weight, stock injectors, stock intercooler, stock converter, stock turbo, ATR exhaust, 108 octane gas, slicks and a "race" chip would go a 12.5x any given day on a 1400 ft altitude track. MPH would be in the 107 - 109 MPH range and dependent on air conditions and tune.

Nowadays, it should be much easier with all the sophisticated chips/hybrid turbos, etc. that are available. I think a TA49 with appropriate injectors, chip, fuel pump, octane, maybe a little bit of converter with slicks and 21-23 psi of boost should have no problems with high 11s/low 12s and perfect driveability.

[buddiiee]

outstanding. thats what im talkin about. but, all that boost kinda scares me. i dont know how good of maintenance the previous owners undertook on this engine, so of course, i just have to assume no oil changes, and the engine runnin hot constantly with the stock rad/thermos. and them gettin on it constantly. abuse pretty much. in addition to the ta49, atr 2.5 duals, new radiator, top of the line stock pos. intercooler, 55lbs injectors or something like around there, sticky dot's, appropriate converter and a better chip to tie it all in, and along with me changing the hood, the trunklid and both bumpers to fiberglass, takin the spare and the whole A/C unit out, and throwin some lightweight gnx rims to top it all off, im estimating maybe 350lbs off the car at that point. so now, could i get high 11's with something under 19 lbs of boost at that point in your professional opinion?

[kenmosher]

Well, I'm not a professional (and I don't play one on TV ) ...


... but, I guess that's one way to do it. Less weight is like more horsepower ... except the fiberglass parts you list are going to be pretty pricey. You can achieve some good weight reduction with the wheels, aluminum drums, sound deadener in the trunk, lighter carpet, etc.

However ... in my opinion, it's not the absolute boost number that makes (or breaks) the car. It's the combination (some turbos don't get even get to their efficient range until 25 psi of boost!) and the tune. You have to monitor things and tune it until you can run the most boost without detonation you can ... and make power. That means a good chip, good octane gas, efficient turbo, careful monitoring with a scan tool, etc.

Bigger turbos, polished heads, unrestricted exhaust, colder air, etc. all help to reduce detonation, but require monitoring and tuning to match fuel and air.