Is my wastegate too small? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 8 Old 08-29-2007, 12:13 AM Thread Starter
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Is my wastegate too small?

Combo is 306, edel. perf heads, Lunati 51014 cam, Holley intake and MP t-70.

I have a TiAL 38mm with 10psi spring, and it will hold 10psi till 4k rpm. Then spikes to 16, down to 9, back up to 16 and back to 9. All this happens between 4k rpm and 5k rpm. I havnt went past 5k rpm yet. Some say the wg is too small, but it seems to be able to regulate after the spikes. Boost ref is coming from right after the compressor.

Im thinking maybe run a 8psi spring and use a MBC set to 12? And run the boost ref farther away from compressor, like say the manifold.

Any suggestions?


80 coupe, N/A 347, tko500 1.34, 6.30 @ 109.01, 9.87 @ 137.06

16 GT, daily driver on pump 93, Procharger 1.42, 6.31 @ 109.59, 9.80 @ 141.57
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post #2 of 8 Old 08-29-2007, 12:11 PM
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boost creep. you may have to increase the diameter of your gate, or add another one.


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post #3 of 8 Old 08-29-2007, 12:56 PM
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I've got a 40mm jgs wastegate on my t70 h/c/i combo and it will hold 8-9 psi all day long at whatever load or rpm. I think that your tial gate should be able to handle whatever your throwing at it.

Is your gate vented into the exhaust or atmosphere? If its not vented to atmosphere, try that and see what happens. Also, try throwing a 8 psi spring in there w/ no controller and see what happens as far as boost creep.

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post #4 of 8 Old 08-29-2007, 01:10 PM Thread Starter
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The gate has a dump tube vented to atmosphere. How could it be boost creep when after the spike, the gate will bring the boost back down? Creep goes up and does not comeback down.

80 coupe, N/A 347, tko500 1.34, 6.30 @ 109.01, 9.87 @ 137.06

16 GT, daily driver on pump 93, Procharger 1.42, 6.31 @ 109.59, 9.80 @ 141.57
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post #5 of 8 Old 08-29-2007, 01:57 PM
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Boost creep is rising boost due to not enough exhaust bypassing the housing. For example, you're set for 13 psi, and when you floor it, you get a quick rise to 13 or 14 psi. But then as rpm's climb, the boost creeps higher and higher: 14, 15, 16, 17, etc.

Spiking is when the hole is large enough to accomodate the boost but the gate is not opening fast enough to let the pressure escape

Not trying to say I know everything ist just that they are two different problems and can both happen together here is something I found on a site.but it sounds like to me you are more having just the spike

A common problem with modded engines is a combination of spiking AND boost creep. That's where you're set for 13 psi, and when you floor if it overshoots to 16 psi, *begins* to drop back down, but as the rpm's rise it goes up again!

Normal boost rise when set to 13 psi = shoots up to 14, then 13, 13, 13...
Spiking = shoots up to 16, then 15, 14, 13, 13, 13...
Boost creep = shoots up to 14, then 13, 13, 14, 15, 16, 17...
Spiking and boost creep = shoots up to 16, then 15, 14, 13, 14, 15, 16,17...
Set a manual boost control to 11 psi and floor it slowly in high gear. It should go to 11 psi and hold it pretty well. If it starts to slowly climb over 11 psi as the rpm's get high, that's "creeping". The boost creeps higher at high rpm's because there's too much exhaust flow for the wastegate hole to bypass.

Now go to 11 psi again, but tromp on it quickly! It will shoot to 13, or 14, or 15 psi, then drop down to 11 and stay there. That's "spiking".

Spiking is a quick flash of high boost that goes a little beyond your set boost point. If you are set for 11 psi, and you tromp on it quickly, this might happen: boost "spikes" to 14, quickly drops to 11, then slowly "creeps" back to 14 or more as the rpm's climb. Now you are seeing spiking followed by creeping!
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post #6 of 8 Old 08-29-2007, 05:04 PM Thread Starter
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How do i fix that???

80 coupe, N/A 347, tko500 1.34, 6.30 @ 109.01, 9.87 @ 137.06

16 GT, daily driver on pump 93, Procharger 1.42, 6.31 @ 109.59, 9.80 @ 141.57
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post #7 of 8 Old 08-30-2007, 12:25 PM
 
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What size I.D. line are you using for your boost reference line going to your wastegate?
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post #8 of 8 Old 08-30-2007, 07:22 PM Thread Starter
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6mm id.

80 coupe, N/A 347, tko500 1.34, 6.30 @ 109.01, 9.87 @ 137.06

16 GT, daily driver on pump 93, Procharger 1.42, 6.31 @ 109.59, 9.80 @ 141.57
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