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WydRyd's Avatar
 
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Question Measuring turbo boost response?

How do you guys guage/measure boost response?

Obviously 1st gear is pretty useless for testing this since there's not enough load on the engine, so what do you guys do to determine boost response?

Discuss please?
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Merv
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Old 11-15-2006, 06:37 PM
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Merv, Look at your rpm's when you hit full boost.

For instance @.7 bar I would have full spool @ 2900rpm, @1bar 3100 rpm's. Oh in second gear or third gear.

Even lower in 4th and 5th.

I have a 4 speed, so for me it is in 2nd.
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Old 11-15-2006, 08:11 PM
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OK, I'll do some time tests this weekend if the weather improves
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Merv
'89 911 Turbo Cab
Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
Old 11-16-2006, 12:47 AM
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I'd do 2nd on a 4 speed.
I've a 5 speed, so I use 3rd and it delivers accurate and consistent results.
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Old 11-16-2006, 07:49 AM
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Quote:
Originally posted by Craig911
I'd do 2nd on a 4 speed.
I've a 5 speed, so I use 3rd and it delivers accurate and consistent results.
Craig, when do you hit full boost?
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Old 11-16-2006, 08:22 AM
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2,700 it is at .7 bar and by 3,000 it'll rip yer lungs out......full boost.

2nd gear in a 4 speed is pretty good for boost measurement, 3rd is even better - but you are HAULING booty in 3rd to measure it sanely.

I measured boost with a factory test gauge (sucker is about a foot across) and graduated in teeny increments. Did mine in 3rd on the 5 speed -
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ -
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Movie: 930 on the dyno
Old 11-16-2006, 08:26 AM
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I am about the same in third....
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Old 11-16-2006, 08:30 AM
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I just attach the LM1 logger and floor it in as high gear as possible w/o killing myself.

Then I park, download the log and examine the curve.

Note, this is measuring boost treshold which has nothing to do with turbo response. Response is a function of shaft inertia. With other words, you can have very quick turbo that comes online late (BB, clipped impeller) or turbo that has lazy spool-up but starts to boost early.

Sounds like an oxymoron but it isn't. Turbo on pic (Mitsu TD05-12G) is one of those that boost early but time time to spool up when "on cam".

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Last edited by beepbeep; 11-16-2006 at 12:52 PM..
Old 11-16-2006, 12:45 PM
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Hi beepbeep,

I think you can easier see the boost thresh-hold if you go in LogWorks to the XY Plot and plot boost over RPM. Then you don't have to put all those measurement points in.

Also another trick. If you also log compressor inlet and outlet temps you can use the LW calculator function to calculate a compressor efficiency trace. Then go to the 3D chart and plot efficiency over boost and RPM. You'll probably find some additional ponies by optimizing the boost curve for max efficiency.

Regards,
Klaus
Old 11-21-2006, 03:11 PM
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