BW 8374 Boost Creep Check
11-28-15, 10:10 PM
#76
I actually have the older tubular manifold, not the cast one. I don't see modifying it for an external wastegate—I'd rather just sell the kit and buy a proper external gate kit. To be honest, it would likely just be a 35R-based kit with a TiAL v-band housing and a single gate plumbed back in. I don't really need to deal with dual gates and all of the associated pain in the *** with plumbing. I'm building a SIMPLE set-up.
It's more likely I will at least try to port this wastegate, open it up to 40mm at least and remove the divider, port the inlet path a bit, and try that out. It will likely depend on the cost of the housing.
The water injection thing has been discussed, but honestly it both goes against the "simplicity" ethos, and if that's where I was interested in going I could just throw that on top of my twin turbos to solve the IAT issue and be done, and sell about $5k worth of stuff.
It's more likely I will at least try to port this wastegate, open it up to 40mm at least and remove the divider, port the inlet path a bit, and try that out. It will likely depend on the cost of the housing.
The water injection thing has been discussed, but honestly it both goes against the "simplicity" ethos, and if that's where I was interested in going I could just throw that on top of my twin turbos to solve the IAT issue and be done, and sell about $5k worth of stuff.
12-01-15, 10:04 AM
#79
What constitutes as sticky tires? I've been tracking for years at ~400whp and have had no such experience with my drive-train. Trans has been fine and my diff, though has a carbonetic LSD has been completely trouble free. No extra cooling, just regular fluid changes.
Edit:
ptrhahn, as you already know I am converting my EWG setup to an IWG. A long with a large streetport, I'll be running a 3.5inch DP, 3.5inch MP to a FEED ti catback. My goal is to hold a steady 15psi for track days and like you I am a fan of simplicity. No AI, E85, etc. Ill report back as to how the system handles my high flow setup and maybe we can compare notes.
Last edited by ArmenMAxx; 12-01-15 at 10:08 AM.
12-01-15, 11:21 AM
#80
It may be down to individual driving style, track characteristics, or just luck, but lots of track guys have noted the phenomenon. Sticky tires would be Hoosiers or other similar slick-style R-compounds
I'll be interested to see how your set up works. This was the purpose of this thread, rather than to psychoanalyze me or my expectations.
One theory I have is that my port is "small" port, mostly intake with very little/no exhaust porting.This is done to maintain exhaust velocity, and I'm wondering if that in combination with an ultra-short manifold, good flow everywhere else, and just a particularly strong motor (as evidenced by making 30-50 more hp than other similar setups), contribute to spinning the turbo up at high rpm. Think of it like putting your thumb at the end of garden hose... the flow of the water increases velocity.
I'll be interested to see how your set up works. This was the purpose of this thread, rather than to psychoanalyze me or my expectations.
One theory I have is that my port is "small" port, mostly intake with very little/no exhaust porting.This is done to maintain exhaust velocity, and I'm wondering if that in combination with an ultra-short manifold, good flow everywhere else, and just a particularly strong motor (as evidenced by making 30-50 more hp than other similar setups), contribute to spinning the turbo up at high rpm. Think of it like putting your thumb at the end of garden hose... the flow of the water increases velocity.
12-14-15, 07:25 PM
#83
None thus far.
Working with Elliot on an extra housing to try porting. I wouldn't expect a definitive answer for a bit, as it'll take a while to get it, figure out how to port it, and pull the kit and reinstall.
I'm also looking at water injection kits—I still don't want to run that or high boost on the track for heat/durability reasons, but having tasted 17psi on the street it would be nice to have that option.
Working with Elliot on an extra housing to try porting. I wouldn't expect a definitive answer for a bit, as it'll take a while to get it, figure out how to port it, and pull the kit and reinstall.
I'm also looking at water injection kits—I still don't want to run that or high boost on the track for heat/durability reasons, but having tasted 17psi on the street it would be nice to have that option.
12-23-15, 12:39 PM
#84
Just to add something on this thread:
I just installed my 7670 IWG on my stock-ish port FC with a turblown cast manifold, 3.5" downpipe, and a small (probably restrictive) air filter.
turbosmart actuator with a 7psi spring
boost is rock solid at 7psi, boost might have gone up to 8psi at redline in 4th gear.
I just installed my 7670 IWG on my stock-ish port FC with a turblown cast manifold, 3.5" downpipe, and a small (probably restrictive) air filter.
turbosmart actuator with a 7psi spring
boost is rock solid at 7psi, boost might have gone up to 8psi at redline in 4th gear.
01-04-16, 12:01 PM
#85
Ptrhahn, I am probably the "other" guy Elliott was referring to. I bought my iwg8374 from him, however I made my own manifold. It is a copy of his. My boost creep is far more severe. On cool days I can see as much as 26psi. I upgraded the ignition to the smart coils thinking I might have been blowing unburnt fuel over the turbine. Didn't work. I also made a 2nd manifold with larger diameter runners thinking there might be a velocity issue. Didn't work. I am dumping a crap load of water/meth in. My knock levels under acceleration never get above the teens. I am running a 100% stock port motor. I was thinking the same as you, too much velocity. At one point I wired the wastegate wide open. Spool up was very slow but still creeped the same above 6k. I have a 3" open exhaust. I put a 2.75" restricter in the exhaust. It didn't change much. A couple of pounds at best. I quit worrying about it sense my knock levels were good. I just make sure to top off the AI tank every time I take it out. I have to say the acceleration is incredible at those boost levels. Please keep us informed if you find a solution.
01-04-16, 12:37 PM
#86
I spoke with an engineer at Borg Warner today, and he indicated that I ought to take a close look at the turbine housing wastegate passage for potential casting issues (wouldn't take much of a booger to plug that 35mm pathway up), and/or if I were to get a 2nd housing to port, swap it in and run it as-is first to compare.
The other suggestion was to run the 9180, because the larger turbine would flow more. BW will make you a custom turbo with the 9180's 80mm turbine wheel, and the 8374's 83mm compressor, but it ain't cheap.
P
The other suggestion was to run the 9180, because the larger turbine would flow more. BW will make you a custom turbo with the 9180's 80mm turbine wheel, and the 8374's 83mm compressor, but it ain't cheap.
P
01-04-16, 12:51 PM
#87
I've looked closely at my turbine housing and WG runners. I really didn't see much room for improvement. There is only a minimum of material that could be removed underneath the door. Like you said, I think you would have to remove the divider in order to gain any amount of area.
01-04-16, 03:16 PM
#88
^ maybe shaving half a mil' off everything would make all the difference? Half a mill on a 40mm hole with a divider in it is quite a bit of material. Is there any way to make the door open further? Move the pivot point on the actuator arm in a touch?
This of course coming from the guy who shat himself and swapped his IWG hotside to an EWG, but I already had wastegates and a manifold to work with. An acquaintance is going to be using one of these and its a bit of a concern.
This of course coming from the guy who shat himself and swapped his IWG hotside to an EWG, but I already had wastegates and a manifold to work with. An acquaintance is going to be using one of these and its a bit of a concern.
Last edited by WANKfactor; 01-04-16 at 03:18 PM.
01-04-16, 03:39 PM
#89
Well, the "door" itself is 42mm, but the diameter of the hole is only 38 or 35mm (I've gotten conflicting info), if you could shave 1-1.5mm around the outside (making the diameter effectively 2-3mm larger, then subtract the divider and the material around the four radiused edges of it, you've got a bit more material.
I'm not knowledgeable about how one would calculate this sort of thing, but taking 4psi off of 16 is 25%, which isn't small.
the 26 lbs of boost that Ernstudet22 is seeing is craziness. It just doesn't make sense that there would be such a wide range (11 to 25 lbs) of results in relatively similar cars. There must be some other factor at play.
I'm not knowledgeable about how one would calculate this sort of thing, but taking 4psi off of 16 is 25%, which isn't small.
the 26 lbs of boost that Ernstudet22 is seeing is craziness. It just doesn't make sense that there would be such a wide range (11 to 25 lbs) of results in relatively similar cars. There must be some other factor at play.
01-04-16, 04:18 PM
#90
Well im guessing that if you took around 0.5mm off the sides of a 38mm hole and divider (leaving plenty there for the door to seat) you'd get about 10% bigger cross-sectional area.
Im not going to pretend to understand the dynamics of wastegat flow and manifold pressure, but I would be guessing that taking into account surface friction on holes that small, 10% more area would equate to more than 10% more flow, especially if you took out even more material than that the rest of the way down the volutes and polished it all up a bit...
Im not going to pretend to understand the dynamics of wastegat flow and manifold pressure, but I would be guessing that taking into account surface friction on holes that small, 10% more area would equate to more than 10% more flow, especially if you took out even more material than that the rest of the way down the volutes and polished it all up a bit...
01-05-16, 10:04 AM
#92
Racing Rotary Since 1983
iTrader: (6)
"a wide range (11 to 25 lbs) of results in relatively similar cars. There must be some other factor at play."
absolutely.
one variable is the turbo manifold. (first off i don't know what manifolds are being used, maybe they are all the same...) if, however, if the do differ they could effect all dynamics.
a well designed manifold will allow the turbo to spool earlier, make more power and therefore be more difficult to control... such as in Peter's case.
a poorly designed manifold will tend to choke the exhaust flow therefore driving the compressor w less net force. the result being an easier to control boost factor.
this may or may not be THE answer but it is a factor. it may prove to be ironic that the manifold is so well engineered from a flow aspect could be your problem.
WG sizing and rotaries
BG engineers are no dummies. WG sizing is walking a narrow line. too small and you can't control boost, too big and you can't control boost.
notice the factors considered by BW when sizing the IWG highlighted in red...
"By using a conservative flow coefficient assumption, we can predict how
much flow will pass through a wastegate port of a specified diameter,
motivated by the expansion (pressure) ratio across the turbine stage.
Using this method, the wastegate can be sized on a match-by-match basis. This
procedure was followed for a wide range of matches (displacements,
power levels, engine speed ranges, turbo sizing) at the beginning of the
project. It was decided that a 31mm port (36mm valve head) would be
sufficient for the smaller turbine housing, and a 36mm port (42mm
valve head) would be used for the larger housings. 36mm may not
sound that much larger than 31mm but in fact it’s 35% more flow area.
nowhere do you see engine type as in piston/rotary.
the rotary produces both more flow and more violent impactful exhaust impulses than the piston engine due to VE and the peripheral exhaust port.
i have no doubt that the rotary requires a different WG setup than a piston engine.
boost creep occurs when WG bypass flow requirements exceed 40% of total exhaust flow.
adding to this challenge is the, uh, diminutive size of the WG.
a 36 mm WG is 1.57 sq inches area
the two exhaust ports are 6.085 sq inches.
i run and recommend a Tial 60 mm WG on my manifold.
a 60 mm is 4.382 sq inches and easily controls boost of a GT4094r at 16 psi.
i do think that with a well flowing manifold, a high energy rotary exhaust flow, a very efficient low mass turbo, a single 36 mm WG will quickly reach a point where it can't bypass 40%.
you are there and i doubt porting the hole will solve your problem.
note BW's statement:
"In extreme cases, the EFR wastegate port will not be large enough. It is
sized to provide capacity for up to 40% of the engine mass flow to
bypass the turbine wheel. However, on applications using very low
boost pressures on large engines, little turbine power is required to
satisfy the boosting task and as a result the need for wastegate flow is
extremely high. In this type of scenario, there may be no other solution
than a very large external wastegate."
Howard
absolutely.
one variable is the turbo manifold. (first off i don't know what manifolds are being used, maybe they are all the same...) if, however, if the do differ they could effect all dynamics.
a well designed manifold will allow the turbo to spool earlier, make more power and therefore be more difficult to control... such as in Peter's case.
a poorly designed manifold will tend to choke the exhaust flow therefore driving the compressor w less net force. the result being an easier to control boost factor.
this may or may not be THE answer but it is a factor. it may prove to be ironic that the manifold is so well engineered from a flow aspect could be your problem.
WG sizing and rotaries
BG engineers are no dummies. WG sizing is walking a narrow line. too small and you can't control boost, too big and you can't control boost.
notice the factors considered by BW when sizing the IWG highlighted in red...
"By using a conservative flow coefficient assumption, we can predict how
much flow will pass through a wastegate port of a specified diameter,
motivated by the expansion (pressure) ratio across the turbine stage.
Using this method, the wastegate can be sized on a match-by-match basis. This
procedure was followed for a wide range of matches (displacements,
power levels, engine speed ranges, turbo sizing) at the beginning of the
project. It was decided that a 31mm port (36mm valve head) would be
sufficient for the smaller turbine housing, and a 36mm port (42mm
valve head) would be used for the larger housings. 36mm may not
sound that much larger than 31mm but in fact it’s 35% more flow area.
nowhere do you see engine type as in piston/rotary.
the rotary produces both more flow and more violent impactful exhaust impulses than the piston engine due to VE and the peripheral exhaust port.
i have no doubt that the rotary requires a different WG setup than a piston engine.
boost creep occurs when WG bypass flow requirements exceed 40% of total exhaust flow.
adding to this challenge is the, uh, diminutive size of the WG.
a 36 mm WG is 1.57 sq inches area
the two exhaust ports are 6.085 sq inches.
i run and recommend a Tial 60 mm WG on my manifold.
a 60 mm is 4.382 sq inches and easily controls boost of a GT4094r at 16 psi.
i do think that with a well flowing manifold, a high energy rotary exhaust flow, a very efficient low mass turbo, a single 36 mm WG will quickly reach a point where it can't bypass 40%.
you are there and i doubt porting the hole will solve your problem.
note BW's statement:
"In extreme cases, the EFR wastegate port will not be large enough. It is
sized to provide capacity for up to 40% of the engine mass flow to
bypass the turbine wheel. However, on applications using very low
boost pressures on large engines, little turbine power is required to
satisfy the boosting task and as a result the need for wastegate flow is
extremely high. In this type of scenario, there may be no other solution
than a very large external wastegate."
Howard
01-05-16, 10:50 AM
#93
Thanks Howard,
The one interesting thing about the BW language is the part about 36mm hole being signicantly larger than a 31mm hole—35%. I don't think thew hole can be enlarged much more than half that 2-3mm, with the existing flapper door. But maybe that's maybe 15-17%. If you then remove the divider, and the radiused edges, maybe you get to the 25% required to get (mine at least) to the safe-margin-on-pump-gas threshold.
It also looks like BW has started making an 9174, but not an 8480... the latter being BW engineer's suggestion to have a larger (and thus harder to spin) hotside.
The one interesting thing about the BW language is the part about 36mm hole being signicantly larger than a 31mm hole—35%. I don't think thew hole can be enlarged much more than half that 2-3mm, with the existing flapper door. But maybe that's maybe 15-17%. If you then remove the divider, and the radiused edges, maybe you get to the 25% required to get (mine at least) to the safe-margin-on-pump-gas threshold.
It also looks like BW has started making an 9174, but not an 8480... the latter being BW engineer's suggestion to have a larger (and thus harder to spin) hotside.
01-05-16, 12:19 PM
#96
that certainly makes sense, I just figured the 7670 would give you the benefits of less heat, less complexity, more reliability (supposedly) that you were looking for compared to the twins...just making about the same HP.
I hope it works out for you, I've been eyeing the switch from twins for a long time and it doesn't seem like there's a bullet-proof single turbo setup for track guys yet. They all have some trade-off. Good luck and keep us posted.
I hope it works out for you, I've been eyeing the switch from twins for a long time and it doesn't seem like there's a bullet-proof single turbo setup for track guys yet. They all have some trade-off. Good luck and keep us posted.
01-05-16, 02:16 PM
#97
I'd port the wastegate. It couldnt hurt. I crunched the numbers and you can get 10% bigger area shaving .5 mm off the openings, and most likely can take more offf than that. It might make all the difference.
Failing that run a small EWg in conjunction or just switch to full EWG hotside with proper twin gates or large single with a divided runner.
Here's me getting all HC on your asses; (actually just working it out here for my own benefit for lack of pen and paper)
area of 36mm wg;
pi18 squre=1,017.9
area of divider assuming 4mm
36x4 = 144
1018-144= 874
area of 38mm circle =1134
3x38mm divider -114
=1020
So that,correct me if i'm wrong, is about a 15% increase from taking 1mm off the ID and .5mm off both sides of the divider. And without having a turbo in front of me, I dare say more can be removed. Im not sure how the extra wastegate flow affects exhaust manifold pressure, i dare say for every small gain in WG flow you'd get a bigger gain in boost control if things were marginal to start with.
Failing that run a small EWg in conjunction or just switch to full EWG hotside with proper twin gates or large single with a divided runner.
Here's me getting all HC on your asses; (actually just working it out here for my own benefit for lack of pen and paper)
area of 36mm wg;
pi18 squre=1,017.9
area of divider assuming 4mm
36x4 = 144
1018-144= 874
area of 38mm circle =1134
3x38mm divider -114
=1020
So that,correct me if i'm wrong, is about a 15% increase from taking 1mm off the ID and .5mm off both sides of the divider. And without having a turbo in front of me, I dare say more can be removed. Im not sure how the extra wastegate flow affects exhaust manifold pressure, i dare say for every small gain in WG flow you'd get a bigger gain in boost control if things were marginal to start with.
01-07-16, 02:40 PM
#100
I spoke again with the Borg Warner engineer, who sent me a few drawings of the housing, and encouraged me to try "Matchbot", they're turbo/wastegate sizing instrument (which is too complicated for me).
One thing that stands out from the drawings sent is the shapes of the two wastegate passages—they don't look at all even to me, or straight. Virtually impossible to port except for removing the divider, which looks to get quite thick in some places further in. It does look like someplace where casting variance could make a lot of difference. He kept telling me to put a boroscope on the passages and look for irregualities—ESPECIALLY with one that won't go below 26psi.
He seems to thing going to a 9180 would actually help, due to the larger hotside, which is sort runs counter to experiences people have (i.e. I've not heard of any boost creep issue with the 7670). I'd hate to lose some spool up time, but the spool is pretty ridiculous with this turbo to start with.
What are the thoughts from the turbo experts on that?
One thing that stands out from the drawings sent is the shapes of the two wastegate passages—they don't look at all even to me, or straight. Virtually impossible to port except for removing the divider, which looks to get quite thick in some places further in. It does look like someplace where casting variance could make a lot of difference. He kept telling me to put a boroscope on the passages and look for irregualities—ESPECIALLY with one that won't go below 26psi.
He seems to thing going to a 9180 would actually help, due to the larger hotside, which is sort runs counter to experiences people have (i.e. I've not heard of any boost creep issue with the 7670). I'd hate to lose some spool up time, but the spool is pretty ridiculous with this turbo to start with.
What are the thoughts from the turbo experts on that?
Last edited by ptrhahn; 01-07-16 at 03:07 PM.