Bigger exhaust ... wonky boost

[chilort]

I'm running a ICd log setup on an '86 Daytona CS (other changes included ported TB, '88 roller cam, FWD Perf Stage 3 GLHS cal, 804 injectors, and a 782 head with 3 angle valve job).

I've had the boost set to 15lbs with the cheapest boost controller I could find.

I found a 2.5" down pipe in the JY and set that up in the car a couple of weeks ago. My overall boost was lower, but no big deal, I figured it was just the change in the setup and I'd fix it later.

Then I decided to build my own 2.5" setup. I got a J-pipe and Magnaflow cat from Summit. I welded it all up, reused the stock hangers that I cut off the original pipe. I'm running a left over Flowmaster (Delta 40 or something like that) from a project a friend of mine was working on years ago. -- I'll have pictures of my setup soon I hope. The only thing that is 2.25 is the section that goes over the axle from the Dynomax kit.

So I took it out for the test drive. I also adjusted the boost controller in a bit to try to get things back to 15lbs where I want it.

In 1st, it goes to about 10lbs, that's it. Then in 2nd and 3rd up to about 13lbs, in 4th it'll go up to about 18lbs then settle down to about 15lbs, then in 5th it goes up to 20lbs and settles down about 17lbs.

How do I fix this? Is it time to get a nicer boost controller?

I've checked for vacuum leaks and have never had an issue. And the car doesn't run like it has a vacuum leak. My lines to the boost controller are as short as I can make them.

Please help...

[1966 dart wagon]

get bigger injectors to use that 'boost creep' to your advantage thats weird it wouldnt boost up higher in 1st and second but my gvalve will creep in the upper gears (4th and 5th). maybe use a gvalve instead? or make the exhaust not flow so good(not good to me) but that will stop it from creeping

[chilort]

I'm freaking stumped here.

[Mopar318]

Some times running a bigger exhaust will reduce the velocity. This velocity can help to keep the turbine spinning or help it to spin up quicker while not under load. Then when under load, the exhaust has unlimited flow after the turbine, which means less back pressure, which means more power, and will cause creep.

This is why larger diameter external gates are real nice.

[turbovanman²]

You need a better boost controller, the wastegate can't control the flow, expecially now you've freed up the exhaust and your crappy MBC makes it worse. I had a customer that was using a cheap one, 91 2.5 Mitsu, spiked like crazy, put a good one on, spiked 1-2 psi and was rock steady thru all the gears.

[chilort]

Any recommendations for a better controller?

I'm thinking one of these
http://store.summitracing.com/partde...5&autoview=sku

[turbovanman²]

Any recommendations for a better controller?

I think I used a "turbosmart" unit, not sure on the price as I "borrowed it" but the local Hipo Rotary guys use's them if not using an EBC.

[chilort]

Thanks!

[chilort]

I picked up this one
http://store.summitracing.com/egnsea...Dbc%2Dhpbc&x=0

(I love living 30 minutes away from Summit).

I set it up and it is like 13lbs in 3rd, 16lbs in 4th, and 20lbs in 5th.

A lot of money spent to not solve the issue.

[Mopar318]

Summit will take it back. IMO your exceeding the limits of the factory wastegate.

[chilort]

I guess I was a little quick to be irked. At least the nicer boost controller is holding the boost rock solid: no creep

Mopar318 -- so you think it is just having a 22 year old waste gate or that even a new OEM version would not handle it?

[Mopar318]

Well I am not sure of the limitations of the gates on these particular cars are. But I have been around other turbo cars since I have been driving. When you start throwing alot of power, and flow at factory stuff, it has a hard time controlling it due to the size of the wastegate.

Alot of times your getting more power with less boost even. So I wouldnt be too discourages as of now.

[WVRampage]

I had issues like that with a mitsu and it was just due to there being to much flow and the wastegate could do its job.Maby you could open the hole up in the turbine housing to get it to flow more.

[bradp]

Do you have the controller hooked to the nipple off of the turbo or from a different vacuum source? The best possible place is from the nipple to the controller, then from the controller to the actuator.

[chilort]

I'm running an ICd log. I don't recall seeing a nipple on the turbo. I'm using the original outlet from the black plastic thing on top of the manifold that originally ran to the solenoid.

The only way the turbine housing is coming back off the car is if I have to take the head off. And let's keep our fingers crossed that I don't have to do that again.

So, basically, if I understand this, the exhaust is now so efficient that the greater pressure drop is essentially blowing the wastegate open early in the low gears. And if I were to have a better wastegate, then it would be able to hold it.

I did go pull on the wastegate shaft and I can pull it out by hand some.

[turbovanman²]

Summit will take it back. IMO your exceeding the limits of the factory wastegate.

No, its controllable with the correct boost controller and his setup makes it harder to control the boost.

I guess I was a little quick to be irked. At least the nicer boost controller is holding the boost rock solid: no creep

Mopar318 -- so you think it is just having a 22 year old waste gate or that even a new OEM version would not handle it?

No, the issue is your setup, a garrett turbo in a blow thru situation is very controllable. If you have it fixed now, then let it be. For the money you spent, I'd rather spend a bit more and use an EBC. I have one now and I will never go back to a MBC. At the track on Friday, I could change my boost on the fly, its awesome,

Well I am not sure of the limitations of the gates on these particular cars are. But I have been around other turbo cars since I have been driving. When you start throwing alot of power, and flow at factory stuff, it has a hard time controlling it due to the size of the wastegate.

Alot of times your getting more power with less boost even. So I wouldnt be too discourages as of now.

Its got to do with being a log setup.

I'm running an ICd log. I don't recall seeing a nipple on the turbo. I'm using the original outlet from the black plastic thing on top of the manifold that originally ran to the solenoid.

The only way the turbine housing is coming back off the car is if I have to take the head off. And let's keep our fingers crossed that I don't have to do that again.

So, basically, if I understand this, the exhaust is now so efficient that the greater pressure drop is essentially blowing the wastegate open early in the low gears. And if I were to have a better wastegate, then it would be able to hold it.

I did go pull on the wastegate shaft and I can pull it out by hand some.

If you don't have a nipple on the comp housing, manifold vacuum is fine. Changing the wastegate won't help, if you go to a blow thru setup, you'll be fine,

[Mopar318]

No, its controllable with the correct boost controller and his setup makes it harder to control the boost.



No, the issue is your setup, a garrett turbo in a blow thru situation is very controllable. If you have it fixed now, then let it be. For the money you spent, I'd rather spend a bit more and use an EBC. I have one now and I will never go back to a MBC. At the track on Friday, I could change my boost on the fly, its awesome,



Its got to do with being a log setup.




If you don't have a nipple on the comp housing, manifold vacuum is fine. Changing the wastegate won't help, if you go to a blow thru setup, you'll be fine,

Oh, I wasnt saying that the factory wastegate cannot be used, Im just saying there is a point where a factory gate can not properly control boost anymore, when you start throwing alot of power at it (more heat, pressure, and volume) I just wasnt sure what that point is on these cars, as I just got mine about 2 weeks ago.

Also what is a log'd setup?

[chilort]

The bottom one is a factory log. It was the earliest intake on the turbo mopars. The runners are extremely short and the plenum is very small.

The top is the intake I bought (I think from a member on this board, but maybe it was "the other one."). It has been modified to make it easier to use an intercooler. The stock intake only leaves about 1" or maybe 2" of space between the intake inlet and the compressor outlet. The compressor housing is also different for the early cars too as it includes EGR.

I personally believe this is controllable. I didn't have this problem until I ditched the stock exhaust for my 2.5" homemade system.

[turbovanman²]

Oh, I wasnt saying that the factory wastegate cannot be used, Im just saying there is a point where a factory gate can not properly control boost anymore, when you start throwing alot of power at it (more heat, pressure, and volume) I just wasnt sure what that point is on these cars, as I just got mine about 2 weeks ago.

Also what is a log'd setup?

A stock Garrett on a blow thru setup is easily controllable.

Log setup is the very first turbo setup, its a suck thru system where as the throttle body is on the inlet side so the boost is sucking on it.

The bottom one is a factory log. It was the earliest intake on the turbo mopars. The runners are extremely short and the plenum is very small.

The top is the intake I bought (I think from a member on this board, but maybe it was "the other one."). It has been modified to make it easier to use an intercooler. The stock intake only leaves about 1" or maybe 2" of space between the intake inlet and the compressor outlet. The compressor housing is also different for the early cars too as it includes EGR.

I personally believe this is controllable. I didn't have this problem until I ditched the stock exhaust for my 2.5" homemade system.

Thats because you made the system flow more air,

[chilort]

Hmmm, okay, so we know the problem. How's 'bout a solution??