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That makes sense. Springs always are force over distance so to get the gate to open up enough to flow more the boost has to creep at higher RPM. So it seems like a pretty straight forward solution is to put a lower spring-rate in then use a boost controller.
Morale of the story is that you really dont want to select your spring based on the boost you want to run at the low end of the spring range. If you want 15 psi it might make the most sense to use a 8-14 or 10-15 psi type spring and use a boost controller to achieve the level you want. Rather than a 12-18 psi spring?
The down side is if you want to run (and hold) higher boost with the car, the lightest spring may be overcome and start to bypass too much gas thus drop boost at higher rpm.
That's what the stocker did on my car. The spring would be overrun at high RPM. Because it's not just static pressure on the gate but velocity pressure at that point (which does not show up on your boost gauge).
It's nice that there is an adjustment on the aftermarket turbos as well to preload the spring.
On my EFR setup I have about to go on I did exactly what you're talking about but hopefully I am fixing the light spring issue.
I have a 2 port turbosmart wastegate. I took one of the springs out so it has a 7 psi spring in it now (they're usually 14 psi which is two 7 psi springs).
I'm also using a 4 port mac boost control valve, so when closed the valve is actually pumping the boost into the bottom of the diaphragm holding the valve closed.
Borg Warner states that all their EFR internal WG turbos ship with the medium boost actuator.
The medium boost actuator has a full stroke psi of 20.6psi.
You aren't even using all of the IWG area you have yet, switch to the low boost actuator for full stroke pressure of 13.7 to 14psi and put a Hallman Pro RX MBC on it to raise the crack pressure.
As noted I've already tried the low boost canister with no preload and it had zero effect. I suspect they are both maxed out or the door is already open as far as is effective.
Although note that the only thing that has had any effect was going from 3.5 to zero turns of preload on the medium canister. Took the boost from 17.5 to 15 or so. Switching canisters did nothing.
BW 8374 Boost Creep Check
So, I've tried everything I can think of and can't control boost creep on my 8374.
Car is a basic set up for track use: Small street port, Turblown IWG 8374 kit, stock coils/twin power, NGK 9/9 plugs, open exhaust, PFC, FFE Step-up kit w. ID2000's, 044 pump.
Speed 1 tuned it, and claimed to be able to hold 15 psi on the dyno, but when I put it on the street, it was 17.5 in 2nd/3rd gear. I took all the pre-load out of the medium canister, and it may have helped a little, then swapped to low boost canister and from a GReddy Ti to a PFS exhaust (more restrictive), that yeilded nothing.. car will hit fuel cut at about 6500 in third. I can see it creeping on the boost trace.
I'm nowhere close to 11-12 psi on spring pressure. I've disconnected the trailing coils to confirm the ignition is working.
For others with the internal gated turbo who are able to control boost, could you post your set ups? Trying to determine if there's anything unique in my setup that would contribute to this, but I'm really convinced it is simply wategate size, and isn't able to waste enough exhaust.
I see now.
Yup, sounds like you need bigger wastegates or a restriction somewhere.
Im running a large street port, Greddy vmount kit, 3 inch DP and Catback with a 3.5" knight sports high flow cat and i have a AEM truboost controller and i can keep it at 10 PSI with only the occasional shudder to 11.5ish in the midrange (dont think this is an issue, likely just a hiccup by the boost controllers refresh rate needing to catch up to a change in exhaust profile) before coming back into control to 10 till redline all on the normal actuator that comes with it. even though i have limited experience in the automotive world, with all the reading ive been doing, it sounds as if some form of restrictor is almost a neccessity with an internal wastegate and from what ive read this would be especially true of rotaries due to their higher EGT's
I think next step, I'm going to wire the flapper open as far as it'll go, and I'm looking into whether there's any indication of a timing issue or harness issue that could be ant-lagging the turbo.
It certainly looks like it's just not enough wastegate, but I did speak with Alex Rodriguez yesterday who runs it with a 3.5" open exhaust with no issues, so it's very puzzling.
If E85 were available here, I'd convert and maybe not worry so much, but I'm already at the ragged edge of pump gas with no tune-ability room. I've absolutely no doubt that if I can get this result in 2nd/3rd gear on the street in 45-50 degree weather, then spinning it out in 4th/5th on a long straight at VIR on a cold November morning is going to see 17-18psi, and start breaking driveline parts.
Question for those more knowledgeable. As I look at the EFR wastegate passage, it would be tough to port because its divided and a shaped channel, so it would be like porting a motor more than just drilling a bigger hole.
What do you think the effect of punching out the divider would be? Divided is nice, but it's not like this turbo has a spool problem, even with zero preload on the actuator. Opening that up would add area to the wastegate, if it did not inadvertently reduce flow through turbulence or something.
Needless to say, I'll be not happy if this is the eventual outcome, but options are narrowing.
On the boost creeping turbo w/ 60mm WG I mentioned I tried to divide the WG passages up to the WG twice. It worked, but the divider would tear from the pulsation between runners (I would have had to cut the tube lengthwise and weld in the divider to make it strong enough).
Anyways, what I noticed on that set up in my data logs (IWG turbo converted to EWG) is that the divider helped the very low rpm boost only (1,000rpm-2,500rpm). Above that there was no difference in data logs or that I could perceive.
So if I would normally have 2psi boost @ 1,500rpm and 3psi boost @ 2,000rpm it would only have 1psi @ 1,500rpm and 2psi boost without the divided wastegate. Pretty big difference by % of boost, but not a big psi difference lost.
At some point it is not lack of exhaust energy causing lag, but rather lag caused by running up against the compressor surge line.
Pics of the boost creeping system I was dealing with-
If I were to port the 8374 I might try first to only port the entrance to the WGs to ease flow into the WG passages (at the cost of a little more turbulence in turbo runners).
If you can't get on a flow bench, what I did was just used compressed air into the turbo runners and feeling the difference of flow between turbo scroll and wg passage. Make sure you fixture the compressor nozzle so it is always in the same place as moving the angle just a bit can really affect the relative flows.
Just keep in mind, I did all this crap to stop boost creep on my FC.
When I had boost creep on my FD I just put in a restriction ("high flow" cat) because it just isn't worth the work and most things besides exhaust restriction you will do to help the boost creep will impact spool just as much.
My opinion from what I have been through. Nothing more, I certainly had the same mind set you did on boost creep the first time around (could not bear a restriction).
Recieved my 8374iwg and TS actuator today (thanks Andy!), planning to start working on it in the morning.
I have all my bits and pieces to fab a manifold, all in 1.5" pipe - would using 2" be better?
Then there is the DP - was going to go 3.5 - would there be foreseeable advantage to having 3.5" DP if i end up running a restricter before the rear muffler compared to staying 3" from the turbo?
Im scrared stiff of overboosting and one-rotor-ing my fresh engine, want to take all precautions possible.
Spoke with Chris Ludwig about a harness via email, and he offered this advise.This looks like a prudent step after I check canister alignment/function and a couple other things:
"Easiest thing for you to do may be to sit it on a dyno as-is and shoot the timing while you make a pull. If you feel it's a timing drift issue, that should show up with a no load rev test as well. I'd check that before swapping harnesses. If there is timing drift, fixing it may be as simple as swapping the the terminals on the crank trigger."
Swapping a harness for an OE harness is an option, but finding a "known good one" may be an issue, so I'm left with buying a brand new one and cutting the secondary injector plugs off at the minimum, or diffing my 100k mile OE one back out, and figuring out what I tore up in the process of this build (which included pirating a couple connectors as I recall). Both seem like a real pain in the ***.
Honestly, that's my thought, but I don't really know how to troubleshoot electronics. The car runs (with and without the trailing coils) and made 430hp @ 15psi, so whatever it is, it must be pretty damned subtle to go un-noticed by me or Dave.
That said, this is the first actionable advice I have to go on—if I can't go into the computer and simply look for a "timing issue", then I need something specific to check, and a specific way to do it.
The car runs (with and without the trailing coils) and made 430hp @ 15psi, so whatever it is, it must be pretty damned subtle to go un-noticed by me or Dave.
Getting spark to the plugs is 1 of 3 critical variables for a tuned car. The other 2 are compression and timing (getting the spark at the right time). You've verified you have spark, so a possible issue with the harness is if it's affecting timing. Are the crankshaft position sensors good, are the connections mixed up (believe the NE and G connectors are the same and easy to get switched up) and do you have a good connection between the connections and the PFC
Also interestingly, in Jacob Cartmill's thread, he said going from a low boost canister to a medium boost canister helped which seems counterintuitive, but if it works....
Finally, believe detonation is a lean condition issue. If you have 2000 secondaries, why not just tune for more fuel flow to compensate for the additional intake charge?
Thanks Elliot,
Once I can get back at the car, I am going to check a few other variables before putting the Adaptronic back in and logging a run—although it's likely not going to be in 4th gear. The speed I'd be traveling at 7k in 4th is too dangerous for a populated area like mine.
We did enough runs before though to know that 12psi wasn't happening with either ECU. I'm going to eliminate things like canister misalignment, and bypass the boost solonoid to ensure that it's passing full pressure along to the actuator.
The one thing that DID have affect was taking preload out of the canister. Three turns = about 2-3 psi, so clearly opening the door further had some affect.
Originally Posted by Turblown
Here is a 4th gear log( street) of Jon's 8374 IWG street ported FD.
This is with a full 3" open exhaust, a pettit medium intercooler, pump gas and the
medium supplied BW actuator. As one can see zero creep issues.
A dual port turbosmart iwg actuator was installed, and this car made 440rwhp @ 17psi on the dyno.
Getting spark to the plugs is 1 of 3 critical variables for a tuned car. The other 2 are compression and timing (getting the spark at the right time). You've verified you have spark, so a possible issue with the harness is if it's affecting timing. Are the crankshaft position sensors good, are the connections mixed up (believe the NE and G connectors are the same and easy to get switched up) and do you have a good connection between the connections and the PFC
Also interestingly, in Jacob Cartmill's thread, he said going from a low boost canister to a medium boost canister helped which seems counterintuitive, but if it works....
Finally, believe detonation is a lean condition issue. If you have 2000 secondaries, why not just tune for more fuel flow to compensate for the additional intake charge?
I've always been told that 15psi is the limit on pump gas (which is all I have access to on the street), and even with race gas on the track this sort of boost is going to break parts.
I want to run 15psi on the street (and did for years on my twins), but I am not comfortable with it being the minimum I can get on spring pressure—that leaves no room top even turn the electronic boost control on as a safeguard for changes in ambient temperature, etc., or to tune the spool up, etc.
Then there is the DP - was going to go 3.5 - would there be foreseeable advantage to having 3.5" DP if i end up running a restricter before the rear muffler compared to staying 3" from the turbo?
From my experience you will have much better spool with 3.5" downpipe/midpipe even if you have to run a restriction at the end of the exhaust to keep boost creep down.
Again on my set-up I originally had 3.5" turbo back with 1 muffler in it. Full boost 3.400rpm. Boost creep. Put tip silencer in exhaust (1.5" hole) same full boost rpm, no creep.
Put 3" turbo back (3" to dual 2-3/8") on with dual mufflers (this was my FC). Full boot 4,000rpm, no creep. Really less boost/torque from idle to 3,000rpm.
Put the 3.5" downpipe/midpipe section on with the 3" to dual 2-3/8" rear section. Full boost at 3,400rpm, great low end again, no boost creep.
I couldn't tell any peak power difference between 3.5" exhaust ending in the 1.5" hole, the full 3" exhaust or the 3.5 down/midpipe to 3" system.
Later when I fixed the boost creep I went back to full 3.5" exhaust and it made the same power on the dyno everywhere as the 3.5" to 3" to dual 2-3/8" (just weighed 30lbs less).
Obviously more power back when boost creeping on the full 3.5" exhaust.
One of the nice things about internal wastegates with electric actuators is that you can set the wastegate valve to whatever position you want. I've had the opportunity to work with these on engine dynos in the past (piston engines) and you learn a lot about boost control that way.
For those of you who don't know, an electric wastegate doesn't have a "spring pressure." All this stuff about canister design, boost control duty cycle and solenoid plumbing, none of that matters. It's just flapper opening angle commands.
One of the things you do for wastegate sizing and matching is a lugging test. So OP try this:
Remove the wastegate actuator completely or otherwise disable it so that the flapper is fully wired open. Whatever it takes to accomplish that. I can't see your setup, but you know what I'm getting at. Mechanically force it open all the way.
Put the engine in 5th gear at 1000rpm. Begin a datalog. Floor it up to at least 4000rpm. I don't know what mph that is with your setup. If you have to do 4th for safety, do that. 4000rpm minimum though. If you can do a 4th gear pull to 7000, do that. Save datalog. Don't do it in lower gears than 4th. You need to lug it. That takes the inertia of the rotating assembly out of the picture.
Repeat test after retarding spark timing (leading and trailing, keep split the same) in the whole map by 2 degrees.
Repeat after retarding another 2 degrees (total: 4 degree retard).
Post datalogs all 3 here. We need to see what your boost curve looks like with the gate forced fully open (something that can be easily done with an electric actuator that we are recreating here). When does it creep above atmospheric pressure? What is the sensitivity to spark timing (turbine energy due to exhaust heat)? I've run these tests before to give turbo suppliers feedback on their wastegate design.
Then if you have the chance you can pop a restricter of some sort into the exhaust if you can. You could also run a more restrictive compressor intake, like a smaller filter. Forget about the intercooler piping, it won't be that sensitive. You can do all sorts of tests here to characterize the wastegate's capacity.
I chased boost creep issues for a while from a cheap ebay manifold and large GT40R. I traced some of the cause to me running very retarded timing (less than 10*) because of 9.7:1 compression.
Just increasing the timing by 2* reduced the peak minimum boost by 1-2psi
One of the nice things about internal wastegates with electric actuators is that you can set the wastegate valve to whatever position you want. I've had the opportunity to work with these on engine dynos in the past (piston engines) and you learn a lot about boost control that way.
For those of you who don't know, an electric wastegate doesn't have a "spring pressure." All this stuff about canister design, boost control duty cycle and solenoid plumbing, none of that matters. It's just flapper opening angle commands.
One of the things you do for wastegate sizing and matching is a lugging test. So OP try this:
Remove the wastegate actuator completely or otherwise disable it so that the flapper is fully wired open. Whatever it takes to accomplish that. I can't see your setup, but you know what I'm getting at. Mechanically force it open all the way.
Put the engine in 5th gear at 1000rpm. Begin a datalog. Floor it up to at least 4000rpm. I don't know what mph that is with your setup. If you have to do 4th for safety, do that. 4000rpm minimum though. If you can do a 4th gear pull to 7000, do that. Save datalog. Don't do it in lower gears than 4th. You need to lug it. That takes the inertia of the rotating assembly out of the picture.
Repeat test after retarding spark timing (leading and trailing, keep split the same) in the whole map by 2 degrees.
Repeat after retarding another 2 degrees (total: 4 degree retard).
Post datalogs all 3 here. We need to see what your boost curve looks like with the gate forced fully open (something that can be easily done with an electric actuator that we are recreating here). When does it creep above atmospheric pressure? What is the sensitivity to spark timing (turbine energy due to exhaust heat)? I've run these tests before to give turbo suppliers feedback on their wastegate design.
Then if you have the chance you can pop a restricter of some sort into the exhaust if you can. You could also run a more restrictive compressor intake, like a smaller filter. Forget about the intercooler piping, it won't be that sensitive. You can do all sorts of tests here to characterize the wastegate's capacity.
I have no idea if this is a step in the right direction, but I like this type of troubleshooting process
Does anyone know if he was able to find a solution? I am curious because I am close to purchase this setup, and before I pull the trigger I wanted to see.
11-16-15, 09:56 PM
