5mall5nail5's Turbo E34 Builds Part II!

[milKt]

Sorry, that's A32guy/Chris' 60-130.

In his sleEk92?

hmmm

[tptrsn]

Sorry, I have no clue about these Vbox times, and a quick search didn't help me all that much. Is this a slow time then?

[SiGmA]

In his sleEk92?

hmmm

With his old e36m3. You know, his non-stock car.

[5mall5nail5]

Def - there are other guys with this exact turbo (Bemdub) regulating down to 12 psi. The problem in my case, I think, having talked to a few people, is a poor pressure differential. I have a T4 with a .81 housing with a 4" downpipe and exhaust. Bemdub has a T4 .81 with a 3" downpipe and exhaust. The pressure in his manifold must be greater in front of the turbine that popping a 44mm hole open causes the exhaust to want to leave. His WG is in the same/worse position as mine (sorry Jon, I mean worse as in further from the collector). We're both venting the back 2 cylinders on the collector. Same with Multiplex except his collector is a lot taller which gives him more common area where the exhaust converges, and is running a T3 GT3582 and a 3" exhaust. So, his pre-turbine pressure should be greater, meaning his exhaust wants to get out his wg, which is in a very near identical position as mine. My T4 4" downpipe must be lower pressure in front of the turbine such that the WG hole opening doesn't really provide that critical of an exit, and so the turbo spools on with the other 4 cylinders not leaving the flow.

When people say the car is slow (its not, but whatever), you can see how the boost curve is lacking when comparing it to when my wastegate diaphragm was torn:



Here you can see 75% throttle position, lower RPMs, and wildly fast spooling turbo. This is the same turbo as I have now. Same exhaust. Torn wastegate, so it was being held closed.

Here is a screen shot of my manual boost controller closed down some (too far, because I was hitting 250 kpa boost cut):



Ideally, if my turbo would hold a level pressure at ANY point, I could hold the wastegate shut by using a solenoid and blocking off the air pressure that will gradually lift the valve in the gate.

What I am experiencing now is, regardless of what psi spring I use, the wastegate vents too little too late to keep the boost down (exhaust doesn't leave out the hole enough). So, with a 2.9 psi spring it would open the wastegate early as hell, making it spool uber slow, but also creep (since the wg placement is less than optimal), peaking about 12 psi by redline. With the 2.9 psi spring, it wouldn't ramp up and hold... it would slowly build like a CF supercharger.

Replaced 2.9 psi spring with a 13 psi spring, since it crept to 12 psi. Boost shot up past 250 kpa (21 psi). It spooled much faster, because the wastegate didn't start to open until later, leaving as much energy in the manifold before opening at the 13 psi. However, since there was all that energy in the manifold and that's what spools the turbo up, more energy coming out of the head, it would creep even faster overshooting the 13 psi by probably a factor greater than the 2.9 psi spring (which crept to 12).

So now I have a 9 psi spring in. That means the WG opens at or around 9 psi, slowing the spool, which is soon enough to keep the engine from making more energy based on incoming pressure, but its not ideal enough to vent exhaust fast/volume enough to stop the thing from spooling, and boost creeps up to redline. Closing the signal off to the wastegate with the MBC means that it spools up a bit faster, but at the same time the energy being produced by the motor is spinning the turbo up and it doesn't stop again.

Here is a screen shot of my holset setup and how I was able to hold boost on that setup:



That was achieved by putting the wastegate in the "up pipe" with a 8.7 psi spring. The T3 turbo created higher pressure ahead of the turbine, and the 3" exhaust contributed as well - when the wastegate would open, the exhaust would want to leak out the hole naturally.

Talking to Mike McCoy - I think rather than making a 2nd wastegate or tying in another tube to my current wastegate, I am going to see if we can tie the current wastegate into the exhaust. Mike said that will help because it will create higher pressure ahead of the turbine and will promote the exhaust in going out of the system into the down pipe.

That is easier than messing with the manifold/collector right now, and if it doesn't work enough, then at least all i did was quiet the car down some, which definitely isn't bad. Hrm.


Ok so looking at my setup here are my two options:



#2 is preferred, because of how I can add a flex tube and such off the WG, and it's easier to tie in, more "wiggle" room if you will. Also it will let me remove the downpipe much much easier. Righ tnow its snug. With that short run off the downpipe in #1 where it ties in, that could prove hard to get the pipe in and out... but...

which is better in assisting the issue? McCoy quit chatting before answering!!!

[tptrsn]

That's interesting about the integral wastegate outlet reducing creep. . . I've wondered whether it would work that way or the opposite. Maybe it's setup dependant, and varies from car to car, or not. . . Seems like while you are reducing the tendency of the exhaust gasses to go through the turbine from having the exhaust system fuller, you are also reducing the tendency for the exhaust gasses to go through the wastegate outlet for the same reason, only to a much more pronounced degree. I mean an outlet doesn't get much more free flowing than straight to the atmosphere.

Before you go and re-plumb your wastegate outlet though, maybe you could try a couple of tuning ideas? Since your motor is built properly for boost, maybe you could tune for a slightly leaner high boost/high RPM area, keeping the AFRs to a minimum of 11.5-ish at the highest boost level (maybe even 11.8 or so). From looking at your logs, I think your rich high end, along with the really low timing you used to run, you could be asking for boost creep by pushing the combustion event out into the exhaust too far. Plug reading and tuning is in order!

Speaking of timing, what timing are you running on this setup? It doesn't seem to be showing in your recent logs, but I see on one of the old ones you were down to around 9 degrees at high boost.

EDIT after looking at your drawings:
I think maybe #2 will be better for wastegate function. The Bernoulli effect creates the lower pressures/higher gas velocity in curves, so that might help scavenge the gasses better. Also, the gas temp will be slightly lower out there, which means . . . . lower velocity? Hrmmm. . . That could be bad I guess. I'll be interested in reading what Mike has to say about this!

[5mall5nail5]

Ignore timing in that old log from the holset, that was a stock motor. I am now running 15 degrees at 18 - 20 psi. Definitely not too low.

[bennyfizzle]

Have you tried putting race gas in it and running 35psi?

Sounds like a good idea to me, for someone else's car

Dooo ittt.

[tptrsn]

Yeah, that is more in line. Did you see my edit in the post above regarding you drawings? I posted it almost exactly when you posted this I guess.

[5mall5nail5]

Thanks tptrsn - yeah I need some pros input. Def? Mike?

Turning the boost up is only a bandaid. Because the spool will still suffer. To run 30 psi I'd probably have to run a 14 - 15 psi spring. That means it would start bleeding off boost at 15 psi, creeping/peaking up to 30. Not ideal. I'd like to run a 1.2 bar spring and regulate it via MBC or EBC up to 30, popping it open when I peak, increasing the spool rate. Look at the spool differences I posted above between when the diaphragm was torn and now.

[gstuning]

Have you tested your piping system for leaks?

I have never , and I mean NEVER EVER seen as 12psi spring allow 21psi boost or anything even remotely close no matter how bad the system is.

For the wastegate routing to be so bad that pressure just doesn´t even go there, it would have to be absolutely terrible, and therefor I don´t think that is your problem.
Cause I have seen much worse do better.

Where is the reference to the wastegate taken from?

[5mall5nail5]

Have you tested your piping system for leaks?

I have never , and I mean NEVER EVER seen as 12psi spring allow 21psi boost or anything even remotely close no matter how bad the system is.

For the wastegate routing to be so bad that pressure just doesn´t even go there, it would have to be absolutely terrible, and therefor I don´t think that is your problem.
Cause I have seen much worse do better.

Where is the reference to the wastegate taken from?

reference for teh WG is off the factory tapped hole from precision on the cold side. Given the system has no problem rocketing the boost up, I don't suspect leaks. All my couplers are adel wiggins clamps with flourosilicone o-rings and lubricant, and my intake manifold is all welded up and tapped NPT with sealant.

The supra guys with similar setups all run dual 44mm wastegates. 4" exhaust, larger T4 turbo...

[Def]

Ok so looking at my setup here are my two options:



#2 is preferred, because of how I can add a flex tube and such off the WG, and it's easier to tie in, more "wiggle" room if you will. Also it will let me remove the downpipe much much easier. Righ tnow its snug. With that short run off the downpipe in #1 where it ties in, that could prove hard to get the pipe in and out... but...

which is better in assisting the issue? McCoy quit chatting before answering!!!

Go number 2, but make sure you join the DP at a close to coincedent angle. This will actually give you a greater pressure differential than just exhausting straight out the wastegate.

Same principle as crankcase evacuation kits to the exhaust. Let the flow of the exhaust drop the total pressure in the WG tube.

Speaking of the reference pressure - have you VERIFIED that the pressure in the reference port off the cold side is reading the same as in the charge pipes. I've seen some tapped holes close to the beginning of the compressor volute not generate as much pressure as later in the volute. Makes sense given you're "packing" air into the volute and that's right at the beginning.

[5mall5nail5]

Def - no I've not noticed, but then wouldn't it just act later? Like, it'd still regulate but just at a different pressure? Not creep like it is.

[Def]

Def - no I've not noticed, but then wouldn't it just act later? Like, it'd still regulate but just at a different pressure? Not creep like it is.

If it was much lower then what you could be seeing is the wastegate opening less at any given boost than it otherwise would.

It's hard to tell without a scale, but does it spool up much faster with the WG completely closed off(you said torn diaphram did that)? It might just be that's what the motor is going to do.

One thing you might try to do to improve spool but still get about the same WG valve opening is to shim a lighter spring. This will improve preload, then once this preload force is passed with the boost pressure*WG diaph. area, you'll get the travel dictated by the softer springrate(i.e. more travel for a given amount of boost/force). Be careful to not shim so much you restrict valve movement by reducing spring travel.

I'd still do the WG tube mod, as I'm a much bigger fan of recirc. WG's. Open WGs are cool and all, but get old.

[gstuning]

reference for teh WG is off the factory tapped hole from precision on the cold side. Given the system has no problem rocketing the boost up, I don't suspect leaks. All my couplers are adel wiggins clamps with flourosilicone o-rings and lubricant, and my intake manifold is all welded up and tapped NPT with sealant.

The supra guys with similar setups all run dual 44mm wastegates. 4" exhaust, larger T4 turbo...

Let´s be honest it´s not exactly rocketing is it?
It get´s there in the very end.

[SiGmA]

It couldn't hurt to test for leaks... Its so so simple, and weirder things have happened.

[5mall5nail5]

I don't suspect leaks because the unit does open and vent and it responds to spring changes. If it had a leak, a 2 psi spring would creep the same as a 9 psi spring, but it's not. All of my fittings are either wiggins or AN If you look at my fuel pressure you see it doesn't wave up and down like a leak would indicate.

I just got off the phone with Howerton Engineering - ordering the HFS6 kit once I get a shipping quote. Should make me feel a little more comfortable with the boost getting up there. Also shot Colbs and email to see if he's around Saturday @ Sparx to let me come over and weld this wg back in. We'll see.

[gstuning]

Try this .

3rd gear
4000rpm
steady cruise
then go WOT and note the lag and report.

That will be a very good indication of where the problem is.

If it´s very laggy then very likely a leak
If not so much but creeps then something to do with the wastegate.

[5mall5nail5]

GStuning - look back at other screen shots from logs. You can see that it's laggy because of the WG opening at 9 psi and creeping. Then when I crank the MBC down it has no problem spooling right up, but overboosting beyond 250 kpa

Here look - with a 2.9 psi spring, the wg is open (I can hear it clearly) and look at the result:



It will build boost (creep) as RPMs go up, wastegate is open at 2.9 psi spring weight, and its laggy because of the spring. So you can't associate lagginess with boost leaks, as the sooner the spring opens and dumps energy, the slower the unit will be to build boost. The spool increases with spring rate, so its not leaking. You can see how ridiculsouly fast it spooled with the torn WG.

[antonch]

It doesn't sound like a leak to me either. The mere fact that you are having problems keeping boost low rather than building pressure up to target suggests that it's not a boost leak.

[5mall5nail5]

Speaking of customer service!

[bennyfizzle]

nice!

[jfdmas]

why did you buy that jon?

[5mall5nail5]

Cause we don't got 100 octane on pump down here

[multiplex]

maybe you don't

also +1 for leak check.