BP gauge
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Post Fiend
Joined: Mar 2007
Posts: 9,010
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From: Johnson City, TN.
Ohhh Now I get it. From the pic where I blanked it out. You wanna know it I'll tell ya but it is just an internet thing. Same with the location I live and my Birth date. all close but no cigar.
Post Fiend
Joined: Apr 2004
Posts: 12,835
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From: Silver Lake Dunes, MI
I would bet that the flutter is just the pulse of each cylinder firing. the turbo does a pretty good job of smoothing the pulses at the plate. either way the flutter I doubt is unusual. Also the dual guage is a good idea!! How about some numbers as far as drive pressures on the turbo. what kind of back pressure do you see with 0,5,10,15,20 psi of boost?
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Post Fiend
Joined: Mar 2007
Posts: 9,010
Likes: 5
From: Johnson City, TN.
The BP is fairly close to the Boost. If I am pushing 10 boost I usually see 8 BP. BP is almost always 2-3 psi behind on accel. Although it is opposite on decel IIRC. Will double check.
I agree the pulses are probably cause due to the closeness to the head and exhaust manifold.
I agree the pulses are probably cause due to the closeness to the head and exhaust manifold.
Post Fiend
Joined: Apr 2004
Posts: 12,835
Likes: 3
From: Silver Lake Dunes, MI
Neal in your talk in the D66 thread about not understanding drive pressures, your BP gauge is exactly what you need to look at to understand drive pressures. The exhuast back pressure is the drive pressure and the boost is the boost pressure. When you have 10 psi BP and 10 psi boost you have a 1:1 ratio. When you Backpressure is higher than your boost pressure say 15 psi BP to 10 psi boost then you have a 1.5:1. the closer to 1:1 the better. With a smaller exhuast housing on the turbo, 1.0 or .84 you raise the BP but also increase the Boost. But it can go too uneven and stress the thrust bearing like Bean stated. When I destroyed my turbo early in the year thats what happened. I pushed 33psi for too long with too thin of oil (rotella 10W30 on a warmer day) and cooked the thrust bearing. so I hope that helps you understand all that a little more. Play with the guages some and you will see what I mean.
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Post Fiend
Joined: Mar 2007
Posts: 9,010
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From: Johnson City, TN.
That is a great explanation. Thanx again. It sounds like when you dumped your turbo it was the oil that cause the biggest part of the failure. Also your boost was quite a bit higher than the BP???? Right?
It sounds like I am already setup to watch for turbo failure. How much of a difference is considered risky. 1.6:1, 2:1? It may be variable whereas 5 psi boost and 2.5 psi BP is not that bad and 20 boost and 10 BP is ba. Does any of that sound correct or make sense?
It sounds like I am already setup to watch for turbo failure. How much of a difference is considered risky. 1.6:1, 2:1? It may be variable whereas 5 psi boost and 2.5 psi BP is not that bad and 20 boost and 10 BP is ba. Does any of that sound correct or make sense?
Post Fiend
Joined: Apr 2004
Posts: 12,835
Likes: 3
From: Silver Lake Dunes, MI
Pretty much for the stock turbo your safe under 25-30 psi of boost. there are many including myself who go over that regularly without harm in the short term. long term who knows. I should also add that the offset ratio I think is the biggest concern in the hgih boost ranges. not so much low boost because the bearing can handle those loads. One of these days soon I need to post pics of my destroyed turbo then you can see how the thrust bearing works and why it fails. IMO its a poor design.
Also with the ratio its higher BP compared to boost that will kill the turbo. the thrust bearing keeps the shaft from forcing too far toward the intake side so the exhuast is the force that needs to be kept in check.
Also with the ratio its higher BP compared to boost that will kill the turbo. the thrust bearing keeps the shaft from forcing too far toward the intake side so the exhuast is the force that needs to be kept in check.
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Post Fiend
Joined: Apr 2004
Posts: 12,835
Likes: 3
From: Silver Lake Dunes, MI
Thanks Jim. Been away for a few days so I am still catching up! Man that takes a long time with. I've eat a field of popcorn too!! I'm thirsty!!
BTW we missed you at Cabelas 2 weeks ago. It was a good day. Too bad the weather was nice! Pics should be posted soon!
BTW we missed you at Cabelas 2 weeks ago. It was a good day. Too bad the weather was nice! Pics should be posted soon!
Post Fiend
Joined: Apr 2004
Posts: 12,835
Likes: 3
From: Silver Lake Dunes, MI
well I also run the 1.0 housing so my BP will be higher than if you have the stock housing. Also that was with my stacks setup on there which I have figured and have since proven was a poorly performing setup. The new stack plumbing will be much improved though after turbo exhaust plays little into BP numbers unless something is clogged.
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