M35 Boost Level

[scotty nm35]

You can measure the boost anywhere from hotpipe to end tanks, to pipe going into the throttle body, they should be all the same. Even when using a Chinese made cooler, there's little pressure drop across the path.

Most gauges measure vac also, which you can only measure from after the butterfly.

[zei20l]

It is in the boot of the car and too cold and wet to get but from memory there is a bolt on either end of the shaft keeping the impella's in place.

thats what i thought! so i find the use of glue hard to believe in a turbo, what glue will handle more than 700odd degrees? i think its to do with the actual rotation of the turbine exceeding a maximum rpm and then coming apart as being ceramic it cant stay together with those forces and heat.

[nickcorr]

Definately glued for the ceramic wheels that I was certain of, on the RB25DET and the Soarer TT engines... Maybe the bolt is to hold it on whilst the glue is curing?

Also don't knock glue, holds the wings on 747's.....

thats what i thought! so i find the use of glue hard to believe in a turbo, what glue will handle more than 700odd degrees? i think its to do with the actual rotation of the turbine exceeding a maximum rpm and then coming apart as being ceramic it cant stay together with those forces and heat.

[zei20l]

hahah i bet it does hold the wings on, but i bet the wings dont get as hot as a turbo

[pixel8r]

Most gauges measure vac also, which you can only measure from after the butterfly.

The factory guage measures vac too so it must be reading it from after the butterfly if this is the case.

There is definitely a sensor before the butterfly which has (in english) written on it "BOOST SENSOR" so maybe this is what lets the ecu know about boost. Pretty sure the s2 stageas had a similar sensor feeding boost pressure signal to the ecu.

Some other interesting info - the s2 stageas (and r34 skylines) had a plastic compressor wheel and ceramic turbine. The s1 stageas and r33's had a steel compressor wheel but still the ceramic turbine i think. Interesting that they went back to metal with the M35. I had heard from many people that the ceramic would let go long before the plastic ever would so it wasn't that bad - and did a good job of making the turbo lighter and therefore spin up faster.

And thanks to nickcorr for mentioning the bit about 747's - I'm never flying again lol

[zei20l]

go on the new airbus 380!!

dont really, apparently they are plagued with problems.

anyway, andy has one he can confirm pretty much anything! and from the pics, it DOES have bolts both end, the compressor wheel is metal. the turbine has too much oil on it to tell what its made from

[iamhe77]

The only answer is to stick it on a dyno and see what you get.

Forgot to answer this one.

140awkw with boost limited to 10psi and my crap compliance exhaust (only 3 cats in at that point) was still fitted.

With the talk about these ceramic exhaust wheels... It is not the itself wheel failing, they are usually fine..

What happens is that when they get get too hot from being over boosted beyond their design limits, the glue holding them onto the shaft fails, and so the wheel falls off, and end up in the cat... This may ping off bits of the turbine. Also the fitment of the plastic intake wheel as on the RB25DET, not sure what it is on the VQ25DET, is not on it's own a bad thing. The plastic wheel is light, and so is able to spin up faster than a metal one, therefore boosting more quickly than a steel wheel equiped turbo.

And if you want to see a ceramic turbo that really hates to be boosted above design specs, speak to the JZZ30 2.5TT Soarer guys, and they have two of them failing...

Not in my instance.

The ceramic wheel was still spinning as per normal, but only 2 blades were present which produced 0.6psi, the rest of the blades as well as some other ceramic bits were located in the dump pipe cat.

[zei20l]

ahhh so they break up from excess heat and too much boost! (no not you anthony)

[iamhe77]

ahhh so they break up from excess heat and too much boost! (no not you anthony)

ahem... stock (11.6psi) boost.

Dunno about excess heat. Ceramic can handle a ton of heat (it is the ceramic panels that absorb the heat when the Space Shuttle re-enters the Earth's atmosphere).

[zei20l]

who knows ay!

i think i want to check my boost tho. see what im pushing

[scotty nm35]

Forgot to answer this one.

140awkw with boost limited to 10psi and my crap compliance exhaust (only 3 cats in at that point) was still fitted.

Not in my instance.

The ceramic wheel was still spinning as per normal, but only 2 blades were present which produced 0.6psi, the rest of the blades as well as some other ceramic bits were located in the dump pipe cat.

So the ex wheel is definitely ceramic, damn.

Could it have been smashed by something coming out of the engine? or... it could have been missing a few blades when imported causing the low boost?

I cant believe 10 psi would cause failure, mine hits 15 psi even with 4 cats.

Car goes in for its 3inch system tomorrow.

[Bis-e Bee]

Car goes in for its 3inch system tomorrow.

Getting a new dump pipe?

[iamhe77]

I cant believe 10 psi would cause failure, mine hits 15 psi even with 4 cats.

I thought you said that your max boost was 0.8bar?

That is 11.6psi.

What did you use to measure the psi?

[scotty nm35]

I thought you said that your max boost was 0.8bar?

That is 11.6psi.

What did you use to measure the psi?

When I bought the car I noticed the dodgy extra cats and asked the owner for a full turbo back system with highflow cat as part of the sale.

I fitted an aftermarket gauge as the car seems to hit boost hard. It confirmed my suspicions. 16psi boost from 3000, 25hg vac.

[iamhe77]

When I bought the car I noticed the dodgy extra cats and asked the owner for a full turbo back system with highflow cat as part of the sale.

I fitted an aftermarket gauge as the car seems to hit boost hard. It confirmed my suspicions. 16psi boost from 3000, 25hg vac.

Interesting...

Pics of your exhaust when it is fitted (or before/during fitting if possible)!

[scotty nm35]

Interesting...

Pics of your exhaust when it is fitted (or before/during fitting if possible)!

Im on nightshift at the moment so I wont be able to hang around while they fit it unfortunately but I will try and get some pics on the hoist.

[andy65b]

I will post some pics of my new exhaust on Friday.

[wht510]

More speculation on the failure mode of the exhaust wheel is needed me thinks.

It could be the following (based on me reading the posts)

1. Higher boost level (go above a boost level and you increase the chance of failure)?

2. Certain kilometers traveled (so for example, hit 100K on the clock and your chances of chewing an exhaust wheel is high?)

2. Boost spike? (over speed of the turbo wheels?)

Possible causes of failure are:

a. increased turbine speed (not sure of the critical speed of the turbo, but perhaps it is linked to 14psi?)

b. Increased heat on both the exhaust and intake side.

c. Cyclic fatigue of the interface between the exhaust wheel and the shaft being different materials, the temperature expansion/contraction will cause internal stresses. Perhaps there is a limit?

____

Just got off the phone to Scotty... Carbon build up on the exhaust wheel bearing, chews out the bearing and bang.

What do you all think??

(Holy thread revival batman BTW!)

[Jetwreck]

Lol...I would agree with most of that.

[zei20l]

carbon build up?

whats the bet the low km cars that come into the country have done short trips all their lives? thus carbon build up as there hasnt been constant heat to burn it all off.

mines still going fine at 117k. but who knows how long that will last lol

it got a bit of a belting friday night and the trip home today.