I am having major boost creep. I am using a 38mm with a .7bar spring on it. On the dyno with the boost controller set at to 15 psi the boost would go to 15psi and then slowly back off to 14psi. On the street with the boost controller off it would hold 10ish psi in 3rd gear but in fourth gear it would boost to 13 and creep up to my boost cut at 17psi. Now with the boost controller on at 15psi it will not hold at all. This is with a .63ar 60trim, full-race ramhorn and 3in exhaust. I will try it with the boost controller uninstalled and the top port of the wastegate open next time. Is the wastegate too small?

 

so on the dyno, it held boost fine and now you are having creep problems on the street?

has anything changed on the setup since the dyno? did you check all your lines and the obvious stuff already?

 

All the lines are good. no leaks and nothing changed since tuning. On the street with the boost controller off it hits boost cut at around 8k in fourth gear only...well havent tried 5th and not going to lol.

 

Yup your wastegate is too small. I have a 67mm and on both, top mount and ram horn I have boost creep even with a 44mm wg. The wastegate is too small to hold low boost...

 

Thats what I was thinking but I did not have this problem with my log manifold. I dont think my turbo is big so that i would need a bigger gate. Is 15psi considered low boost?

 

Yup, its considered low boost. I had the same problem a while back. The manifolds are so efficient and flow so well that to much air flows past the wastegate. Do yourself a favor if you want to keep it and have it work properly. Send it back and have it reflanged for a Tial 60mm. Its the only way you'll be able to control low boost. Its either that or dual 44s. Trust me, its your only options if you want to keep that manifold and control low boost properly.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SpoolnG2 &raquo;</TD></TR><TR><TD CLASS="quote"> Send it back and have it reflanged for a Tial 60mm. Its the only way you'll be able to control low boost. Its either that or dual 44s. Trust me, its your only options if you want to keep that manifold and control low boost properly. </TD></TR></TABLE>
This might be the case but why would hold on the dyno?

 

Because there is more load on the motor when your driving it on the street, along with different air temps and densities. Which is why when you dyno tune a car the a/f becomes more lean from the dyno to the street.

 

i run 26psi on my 38mm wg

no problems

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gisserhatch &raquo;</TD></TR><TR><TD CLASS="quote">i run 26psi on my 38mm wg

no problems</TD></TR></TABLE>The higher the boost the better....

 

Exactly, the higher the boost the less exhaust that has to exit. Which means a smaller discharge (38mm) is ok.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 007EG &raquo;</TD></TR><TR><TD CLASS="quote">Exactly, the higher the boost the less exhaust that has to exit. Which means a smaller discharge (38mm) is ok. </TD></TR></TABLE>

its not actually that simple but it is somewhat correct. as boost increases the amount of exhaust being created increases, a lot of that still has to flow out of the WG...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">its not actually that simple but it is somewhat correct. as boost increases the amount of exhaust being created increases. . .</TD></TR></TABLE>
This statement gets at something I've been trying to nail down for a while as I get ready to put a setup together (trying to figure out how much wastegate flow I needed).

So from this thread I guess the consensus is that: More exhaust flow is created as you go higher in boost, but the additional exhaust flow still tends to be routed more to the turbine to make the higher boost than to the wastegate, and thus the demand for wastegate flow capacity is reduced, not increased.

Bottom line from this hypothesis then ins that lower boost conditions tend to need a larger wastegate flow capacity to hold steady than high boost applications do.

Agreed? ? ? ? . . . . . . ? ? ? ?

Edited: because I didn't like my wording the first time around.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SpoolnG2 &raquo;</TD></TR><TR><TD CLASS="quote">Yup, its considered low boost. I had the same problem a while back. The manifolds are so efficient and flow so well that to much air flows past the wastegate. </TD></TR></TABLE>

Or you could consider it poor wastegate placement. Cars make their usable power with the wastegate open - it's okay to feed the wastegate instead of trying to ignore it. Look at how they did the old F1 cars, fed both turbine and wastegate via a 20-30 degree divergent collector.

 

Several people say they would rather sacrifice using a larger wastegate and the placement of it then not having the majority of the air going straight to the turbo. I agree b/c its a pain in the *** to buy a 60mm wastegate of dual 44s just b/c of bad placement. But every single manifold is just like that. So what do you do ?

 

There's a lot of turbulence at the wastegate port whenever the wastegate is open. There are no gains/losses in efficiency from the turbo at this point (wastegate open), merely intelligent design so that you don't have to drop $1.9 million on wastegate(s) when they aren't needed. We can make a mathematical statement for it, where the two situations are equal only in cases where wastegate price doesn't matter:

Flow is going to be obstructed more by wastegate turbulence when there's a straight shot at the turbine = Flow is going to be diverted away from the turbine by wastegate port placement.

I've seen a number of manifolds with the wastegate port angled slightly, it makes a bit of difference in whether or not a 38mm wastegate and low boost flies or not and you won't see any appreciable difference in power/efficiency between the setups.

 

I agree with your statements, but my question is why do so many manufactures not fix this problem on their manifolds and just leave them at basically a 90 degree angle? Seems like almost every equal length manufacturer has similar problems. Dont you agree?

 

It's easy to do as you don't have to holesaw at funny angles, it's familiar and doesn't create a fuss, and most importantly it's bandwagon approved. Plus, when a dozen reputable companies say it's required people listen and take it as the One True Answer despite some notable exceptions like HyTech, etc.

Meh, truthfully, nothing is ever that cut and dry. An example:

For something like the FR long runner K-series offerings that put the turbo above the transmission, which is a design the big boys need to make power, you have to run twin 44+ (preferrably 50, in my experience twin 44's with 11 psi spring creep to around 15 psi) mm gates with GT40 or larger turbos. One look at how things have to be packaged in those cars and it's a neccesary evil, and is how you do things "correctly" for those cars. However, (again in my experience) a single 44mm gate is plenty to maintain 11 psi with a GT40 on a B-series where there is a bit more room to do things "correctly."

Sometimes I split hairs over things that don't matter, especially when taken in light of the fact that EVERY build is assembled from compromises. I don't think this is one of those situations, though. Popular design inefficiency forces the customer to purchase a couple hundred dollars of supporting gear that isn't required in a correctly engineered solution.

Anyway, just my opinion. Thanks for nobody being reactionary and turning this into a flame thread, which is how manifold discussions used to go down in this forum.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tjabo &raquo;</TD></TR><TR><TD CLASS="quote">
This statement gets at something I've been trying to nail down for a while as I get ready to put a setup together (trying to figure out how much wastegate flow I needed).

So from this thread I guess the consensus is that: More exhaust flow is created as you go higher in boost, but the additional exhaust flow still tends to be routed more to the turbine to make the higher boost than to the wastegate, and thus the demand for wastegate flow capacity is reduced, not increased.

Bottom line from this hypothesis then ins that lower boost conditions tend to need a larger wastegate flow capacity to hold steady than high boost applications do.

Agreed? ? ? ? . . . . . . ? ? ? ?

Edited: because I didn't like my wording the first time around.</TD></TR></TABLE>

i agree

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SpoolnG2 &raquo;</TD></TR><TR><TD CLASS="quote">Yup, its considered low boost. I had the same problem a while back. The manifolds are so efficient and flow so well that to much air flows past the wastegate. Do yourself a favor if you want to keep it and have it work properly. Send it back and have it reflanged for a Tial 60mm. Its the only way you'll be able to control low boost. Its either that or dual 44s. Trust me, its your only options if you want to keep that manifold and control low boost properly. </TD></TR></TABLE>

I run a single synaptic 50mm gate on a ramhorn and can hold boost to 5 psi(+- .5psi) with my sc61 1,2,3,4 gear, till redline. dual 44's and a tial 60mm is probally a bit bigger than he needs, id like to see the synaptic 40mm on his setup and see what it does.

 

When was it tuned?

ambient air temperature might have a role in your problem as well

As in. it is colder now so now your controller might need to be reconfigured.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Riake &raquo;</TD></TR><TR><TD CLASS="quote">When was it tuned?

ambient air temperature might have a role in your problem as well

As in. it is colder now so now your controller might need to be reconfigured.</TD></TR></TABLE>

Good point.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SpoolnG2 &raquo;</TD></TR><TR><TD CLASS="quote">Because there is more load on the motor when your driving it on the street, along with different air temps and densities. Which is why when you dyno tune a car the a/f becomes more lean from the dyno to the street. </TD></TR></TABLE>

 

The pressure will have a small effect, but not dressing the IAT corrections is a problem with the tune not with using a dyno to tune with.

Everything that sees a dyno needs to see pavement to solidify a tune.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Riake &raquo;</TD></TR><TR><TD CLASS="quote">When was it tuned?

ambient air temperature might have a role in your problem as well

As in. it is colder now so now your controller might need to be reconfigured.</TD></TR></TABLE>

It was tuned about 3 weeks ago at night with ambient temps around 50 degrees. the weather has been consistent since then keeping the temps around the same.

UPDATE:
I unhooked my boost controller and left the top port on the wastegate open and boost seemed to hold at 10ish psi although I did not rev it out to see if it would creep even though at around 6500 boost was already at 13 psi before. I will try to get a good pull after work today if there is not too much traffic and see.


Modified by champLSinteg at 12:31 PM 1/2/2008