Ways to lower my spool-up rpm?

[FattyBoomBatty]

I have a regular 6262, journal bearing turbo with a .82 t3 exhaust and 3" v-band out.

I have a cast log manifold, stock valves in an unported head.

I would like to lower the spool-up rpm. Right now I can get full boost around 4200rpm and would like to get it as close as possible to 3500rpm.

I have thought up some ways to do this, including shorter intercooler piping/different I/C location, changing to a divided header and turbo. Sizing options for divided t4 housings for the 6262 are pretty limited, and when I called PTE, he said I'd be going in the wrong direction with a .84 divided t4 housings, the smallest one they offer for the 6262.

So what can I do? I considered replacing the current turbo with their full CEA ball bearing version, it would be pretty expensive just to reduce spool-up time, but it's also better in other ways. I've read that ~1.0 A/R t4 divided housings were comparable to .82 T3 ones when it comes to spool-up rpm, but that's not what the rep at PTE said. Can anyone give some insight?

I would go with a smaller turbo, but goals for the car, HP wise are 600+.

[Goat Blower]

Stroker.

[FattyBoomBatty]

not really any stroker kits for my engine, haha.

[Goat Blower]

2.4 4G64 wide bellhousing mount, 2G head. Or the simpler route might be an adjustable cam gear and shift the power band a bit to the left, you might give up a bit of top end though.

[FattyBoomBatty]

I'll just stick with the motor it's got. The intake manifold will stay about the same, as well as the cam. Other head work and new valves will be put on later, but for now I'm mainly trying to focus on exhaust side mods and tuning. Have you ever done before and after logging or dyno when doing mods, especially to the exhaust side? Anything from valves to porting, headers, different exhaust housings and larger diameter exhaust tubing?

[Fran05]

4200 is actually pretty good rpms to spool that thing. What boost are you running?

[FattyBoomBatty]

around 24 or 25 until I upgrade the clutch, but then 30-35 or whatever. 4200 rpm might be good on a DSM/evo, but they also usually rev 1000 rpm higher than I do.

[Pushit2.0]

Setup anti lag, try tunning the car for better spool up, use a 35 shot of nitrous.

Lag for the most part is inertia. Going bb would not gain much in initial spool up but between gears is where they shine.

The t4 divided housing are a little smaller then open housing with the same a/r. And the housing will have more of an affect on power band.

[FattyBoomBatty]

As far as racing is concerned, I upshift right into the powerband, so it's not that it's too high. Just looking to make it more "fun". I am really really leaning toward divided housing. So what you said about them being effectively smaller than the same size open housing is nice. I talk with a guy in Illinois alot who has a gt40 turbo on his car with a .96 divided housing. His whole setup is a little different than mine, but he was claiming full boost at 3800rpm.

I just don't know what to think about the housings because I've heard conflicting stories about how they affect the engine in a comparison scenario.

As for tuning, I was thinking a header would allow me to run a bit more timing, which might help spool up. I believe there is lots of room to play around with the tune, especially with a couple different parts.

[Kracka]

Smaller turbo, you don't need 600+ on the street.

[tpunx99GSX]

Originally Posted by Kracka

Smaller turbo, you don't need 600+ on the street.

Says Who?

[Kracka]

Me.

[tpunx99GSX]

Originally Posted by Kracka

Me.

Who do you think you are?

[Kracka]

Krackasan.

[Shane@DBPerformance]

BB will not spool it quicker initially. Cams, ported head, tubular manifold will likely make it laggier. A .63 A/R exhaust housing might spool it 300-500rpms quicker. Bigger/less exhaust after the turbo will help spool quicker. Coating the exhaust manifold and turbine housing will help keep heat in and spool quicker.

If you remove ignition timing in the spool up areas it will spool faster, but you can get to the point where it spools faster, but makes less power than if you just had reasonable ignition timing and less boost.

[Speedfreak]

Tuning the wastegate? When I was sold the wrong springs for my wastegates without knowing(way to heavy), I noted that spool was sooner and quicker(on Shanes dyno) than previous runs. Meaning if you put pressure(boost) to the top of the wg I'm guessing you could possibly keep it fully closed until you need to regulate the pressure and thus create the same effect? For reference, when I got the correct springs, it spooled slower and later.

Just a theory, but I believe its done already by some?

[Goat Blower]

Originally Posted by Speedfreak

Tuning the wastegate? When I was sold the wrong springs for my wastegates without knowing(way to heavy), I noted that spool was sooner and quicker(on Shanes dyno) than previous runs. Meaning if you put pressure(boost) to the top of the wg I'm guessing you could possibly keep it fully closed until you need to regulate the pressure and thus create the same effect? For reference, when I got the correct springs, it spooled slower and later.

Just a theory, but I believe its done already by some?

That was the main idea behind those fancy electronic boost controllers everyone used back in the day. I don't hear anyone using those much anymore.

[1QUICK4]

N2O?

[Shane@DBPerformance]

Manual boost controllers usually spool faster than electronic, unless the electronic is setup to stay shut and not start pulsing until the last moment.

[Goat Blower]

Originally Posted by Shane@DBPerformance

Manual boost controllers usually spool faster than electronic, unless the electronic is setup to stay shut and not start pulsing until the last moment.

I thought that was the benefit of the HKS EVC2? Shep and some others were all using it at one point ~10 years ago.