Blow Off Valves Fact vs. Fiction

NoCoast Wrote:
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> Turbos were from TEC here in Denver before the
> owner committed suicide.
>

Well maybe all the blown turbos had something to do with that.

I could never get a straight answer out of that guy when i tried to get specific Garrett parts to make turbos for the Xratties, very vague.....
> Grant Hughes
> www.nocoastmotorsports.net
> Denver, CO

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John Vanlandingham
Sleezattle, WA, USA

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token-negro Wrote:
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> >
> You can hear it in car really well with this
> video. 35r Turbo 500+ whp NO BOV


A 35R has the anti surge slots thing (name?) where it bleeds air from the outlet back to the inlet so you can run a turbo that is way too large for your engine without running into the damaging kind of surge shown in that one linked video. I think they call it a map width enhancer.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

This has been all very educational but since there's a BOV already installed, I think I'll just keep it there for the nonce...

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Jay Woodward
Snohomish, WA
'90 Mazdog Frankenprotege
Chronologically, 46...

Pete Wrote:
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> token-negro Wrote:
> --------------------------------------------------
> -----
> > >
> > You can hear it in car really well with this
> > video. 35r Turbo 500+ whp NO BOV
>
>
> A 35R has the anti surge slots thing (name?) where
> it bleeds air from the outlet back to the inlet so
> you can run a turbo that is way too large for your
> engine without running into the damaging kind of
> surge shown in that one linked video. I think
> they call it a map width enhancer.
>
> Pete Remner
> Cleveland, Ohio
>
> 1984 RX-7 (rallycross thing)
> 1978


Not true, most 35r turbo's out there came witout a ported compressor housing. ATP among others had this as an option but for many just ordering a 35r you would get one without. Now the GT30 always came with a ported compressor housing from Garrett.

Hmm, okay. Did not know that.

The ones that Perrin sells have the ports.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Yep Perrins did for a good while and then didnt. Now ATP or Garrett themselves offers it as a casting option. A few places do there own version, like Tial they machine there own type that looks more like the 30r's. Its a worthwile option for sure. Heres a picture of it for people who dont know what we are talking about.

I've always used a T-04 turbo in the Volvo sized for a boost threshhold of 3000 rpms.

I never had issues with my turbo until we installed an intercooler that was too small. I believe that this made the turbo surge and blew it up. This was in August of 2009 or so.

My turbo dates to 1998 or 1999. I sure can't complain about that being a source of trouble and no bypass valve for me.

When abusing the car on stage the engine is always between 4000 and 6500. Lag? Not that is noticeable.

My turbo came from Turbo Engineering Corp. Reads as though some have have had a different experience of their turbo that came from TE.

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JohnLane

Overkill is consistently more fun

if there was no benefiet then, im curious why most factory systems have some form of bypass (albiet early turbo cars did not, but they also have no intercooler msot of the time and ran minute amounts of boost). Has to be some truth to the end relibility. But for racing purposes...

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I think that's exactly it - a manufacturer would like to add reliability over the life of a standard consumer vehicle.

Plus, on cars with short-ish inlet system you can cause stalling airflow on the inlet side wreaking havoc with MAF-sensor-based fuel management (throttle plate closes, pressurized side bleeds pressure out through the compressor to the inlet side, MAF registers zero air flow).

Someone else already said it perfect. It's basically no work to tune, costs next to nothing, rarely fail, and may enhance turbocharge longevity and improve performance between shifts.

On a dedicated race car (such as WRC) where you are putting in new turbos as a PREVENTATIVE maintenance item per race day (nice to have that sort of resources...) then it probably doesn't make any discernible difference.


edit: Also, this might be a great thing to experiment with. If you're using a ball bearing turbo that can withstand a bit of abuse, try plugging the vacuum line (so the valve can't displace any air and open) and see how it drives. You may have to adjust your tip-in (acceleration enrichments) to compensate for the two modes. You still running MS right?

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http://www.ckrally.com



Edited 1 time(s). Last edit at 03/25/2010 03:16PM by cblakely.

Funny part is I have two BOV's, I just want one less failure item, one less thing to fix at service or to fail on stage.

We are still on Spitfire EFI, so tuning for either shouldn't be an issue, as long as we have time before Oregon Trail.

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-Tom
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Leave it out Tom.

I'm betting that you won't miss it.

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JohnLane

Overkill is consistently more fun