How bad is the turbo lag for autox/rallyx?

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czei
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How bad is the turbo lag for autox/rallyx?

Post by czei » Thu May 07, 2015 12:00 am

I'm thinking of getting a turbo Legacy for rallyx, predicated on bumping the torque/HP with some mods. (My current rallyx car has a 2.5L engine in it.)

On paper the mod'd 2.2T should have better torque and HP than the 2.5L, but at what cost in lag? Are people just putting on giant turbos and waiting for them to spin up?

I've driven a stock bug-eye WRX and the turbo lag on those is too slow for rallyx-- how is the Legacy lag compared to that?

Thanks!

mike-tracy
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Re: How bad is the turbo lag for autox/rallyx?

Post by mike-tracy » Thu May 07, 2015 12:28 am

I have driven bone stock SS's and 2.0L bugeyes, but never back to back. My impression of the ej22t/vf11 combo is there's virtually no perceptible lag. The turbo's spool is close as instant as can be, unless you miss a gear, going from 1st to 4th for example.

The turbo sizing, as well as the 22t's restrictive heads and exhaust lends it to great and immediate low end grunt.
1992 Legacy SS 5mt, build in progress
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MConte05
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Re: How bad is the turbo lag for autox/rallyx?

Post by MConte05 » Thu May 07, 2015 3:09 am

There is a reason I've been sticking to the small VF11 on my rally car. Could I stick a 16G or a TD04 on it and get that bump in power? Sure. Is it worth the tradeoff of nearly instant boost? Nope.

My car while underpowered compared to a typical "open class" car, drives with excellent response.

Watch the boost gauge in these onboard clips.


czei
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Re: How bad is the turbo lag for autox/rallyx?

Post by czei » Thu May 07, 2015 3:19 am

Thanks, great video! The resolution isn't enough for me to tell what the boost gauge is supposed to be showing. Plus, I've never owned a turbo, so it wouldn't have made a difference.

How do you you have your car setup, i.e. transmission, engine config, etc?

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Re: How bad is the turbo lag for autox/rallyx?

Post by MConte05 » Thu May 07, 2015 6:07 pm

It's set to 12psi, anything over that with the little VF11 and you are just blowing hot air.

It is a standard 1991 2.2 Turbo, stock exhaust, open downpipe, and a custom elbow with a big K&N filter. Otherwise just a RobTune ECU. Nothing fancy at all.

Trans is a 4.44 JDM STI trans with Cusco 1.5 way front and rear differentials. Which the diffs are amazing for stage rally, but for rallycross a plated front diff will just cause a lot of pushing. Plated rear will make it a hoot.

czei
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Re: How bad is the turbo lag for autox/rallyx?

Post by czei » Thu May 07, 2015 8:31 pm

Thanks for the info, that helps a lot. I just missed buying a 5MT STi transmission, and am still trying to figure out what to do. Are you running the DCCD as well?

What's your opinion of the drop in 12kfg and 20kfg center diff options for the 5MT transmissions?

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Re: How bad is the turbo lag for autox/rallyx?

Post by Mister Anderson » Fri May 15, 2015 3:54 am

Awesome videos dude! I really want to auto-x my car when I'm finished with it this summer. I have a STi-RA 5 speed trans /DCCD with the plated rear end so it should be a blast.
91 black SS 5 speed.... 300k on engine.
93 silver TW 5 speed... Track car project
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MConte05
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Re: How bad is the turbo lag for autox/rallyx?

Post by MConte05 » Fri May 15, 2015 1:52 pm

The upgraded diffs will be great for track (legitimate track) and rally duty. But for RallyX/AutoX it's just going to cause too much understeer that will be tough to work around. I still have the 4kfg stock center diff in my rally car. I'd love to do a DCCD upgrade, but always on the lookout for a 12kfg diff. 20kfg with my power output would be just too much.

I'm jealous of that RA trans. That's about as good as it gets!

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