Too much lag and only 5psi of boost! Please help!!!
Fixed all leaks. I swapped the cam out for a VTC-3 cam from Virginia Speed. I took it out for a road trip today to work on the tuning. I will post up my results. The cam should help it out alot. This cam should realy help the bottom end power and help to make the turbo spool. I will let every one know how it does once the tuning is done.
Last edited by Texas_WS6; Jan 21, 2010 at 12:08 PM.
Yes sorry for the delay. I have the cam in and I started tuning on it again. The car drives 100% better. I realy like the way it is running now. It still is not perfect. The cam did help with the lag time but it is still too much lag. I ordered a new turbine housing. It should be delivered tonight. I am going from a 1.08 AR T-6 flanged housing to a .96 AR T-4 housing from Precision Turbo. I think this will fix my lag time. I have reworked so many different things in this and it is still not just right. I am begining to think I went too large on the exhaust piping (3" Wrapped) and too large on the turbine housing. I am hopping the new housing will fix my lag time and limited boost. If it still lacks a little then I guess I will redue the exhaust to 2.5" like Forced Induction told me I might have to do.
Something I have noticed here, I have driven my car to Odessa two different times since I replaced the cam. Odessa is about 100 miles from me and our elevation is close to 3900 feet while Odessa is close to 3200 feet. In Odessa the turbo will build boost to 6.5psi while it will only build 5.5psi here. I am thinking part of the reason I am having issues with limited boost is the elevation. Thats why I am down sizing the turbine housing to a .96AR. I will know more this weekend. If the housing fits correctly I am going to start changing everything out tonight and I plan on being finished Saturday or Sunday. I should know more by then. I hope to have everything done Friday night so I can take the car to Penwell Raceway Saturday and start tuning it. If I make it I will be tuning my car and a friends 98 Camaro with a 6.0L and D1SC.
Something I have noticed here, I have driven my car to Odessa two different times since I replaced the cam. Odessa is about 100 miles from me and our elevation is close to 3900 feet while Odessa is close to 3200 feet. In Odessa the turbo will build boost to 6.5psi while it will only build 5.5psi here. I am thinking part of the reason I am having issues with limited boost is the elevation. Thats why I am down sizing the turbine housing to a .96AR. I will know more this weekend. If the housing fits correctly I am going to start changing everything out tonight and I plan on being finished Saturday or Sunday. I should know more by then. I hope to have everything done Friday night so I can take the car to Penwell Raceway Saturday and start tuning it. If I make it I will be tuning my car and a friends 98 Camaro with a 6.0L and D1SC.
The housing did arrive today. I just swapped them out. The PT .94 T-4 housing fit perfectly. Man it is allot smaller then the 1.08 AR housing I had on it. I am going to start modifying the piping going into the turbine housing. I have to cut off the T-6 flange and install the T-4 flange. I hope this fixes the lag and the limited boost! I am sure the lag will be gone now, but I am not possitive it will fix the limited boost yet.
I think Precision told me this will make my GT-88 like their PT-8847 or PT-4788, something like that. I emailed them and asked them to clearifiy that for me. I will post up what they say.
I think Precision told me this will make my GT-88 like their PT-8847 or PT-4788, something like that. I emailed them and asked them to clearifiy that for me. I will post up what they say.
also, FWIW, i had the same problem with a front mount t70 on my first turbo build. What it ended up being was I had a blown header gasket that wasnt completely blown. every pressurized test I did showed no leak, but it leaked enough when it got hot to effect spool up. I dont think yours is the same issue though and I look forward to seeing how it goes for ya.
Ok, here is the latest update. I finished installing the new smaller .96 AR housing along with the piping modifications for it. Now I can realy hear the turbine were as you could not hear the turbine at all before. The lag time is very close to gone now. Just were I wanted it to be. It comes on nice and hard very soon. So I will call the lag time fixed. But.....
It still is not making any more boost then before. I did not want to do this but I guess I will have to now. When I get back from the track (I am not taking my car) I will pull the wastegate sensing line off the wastegate (and yes plug the line from the manifold) and give it a try. Yes, I will be watching the boost gauge and if the boost climbs over 10psi I will back out of it. This test will tell me without a dought if the wastegate is opening or not. If it makes boost then, then I will just put my other springs in the gate. If it still does not build any more boost.... well I do not know what to do next.
No point in speculating what to do if it does not build any boost. I will just have to see what happens first. I did not try playing with the springs in the gate because I was trying to fix the lag issue first.
I will report back on Sunday after I have a chance to test the gate.
It still is not making any more boost then before. I did not want to do this but I guess I will have to now. When I get back from the track (I am not taking my car) I will pull the wastegate sensing line off the wastegate (and yes plug the line from the manifold) and give it a try. Yes, I will be watching the boost gauge and if the boost climbs over 10psi I will back out of it. This test will tell me without a dought if the wastegate is opening or not. If it makes boost then, then I will just put my other springs in the gate. If it still does not build any more boost.... well I do not know what to do next.
No point in speculating what to do if it does not build any boost. I will just have to see what happens first. I did not try playing with the springs in the gate because I was trying to fix the lag issue first.
I will report back on Sunday after I have a chance to test the gate.
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What exhaust manifold gaskets are you running? I am using the GM gaskets right now. They are not much more then a thin peice of stampped steel. I if removing the wastegates ability to open does not make more boost then I will try and pressure check the system hot some how. I have not seen any stains on the heads like exhaust residue, but I will recheck. My gate does have alot of exhaust residue on the outlet like it has been opening.
Well pull the gate line and see whats up. If gate is sticking partially open that is another idea.And if not that then its back to finding boost leak or you have hurting turbo ,leaking blow off,something is doing it.
Yep, I just got back from the track today. We only had 3 passes for me to tune the car. It ran 10.68 at 128mph on 14psi with 160 degree IAT and 13.5 degrees of timing. Not too bad for a full weight 6.0L F-body first day out at 3200 feet. I think with the methonal kit installed we can get that temp down and keep going up on the timing, I see 9's around the corner!!!
While we were there I spoke with Turbo383WS6 about what was going on with my boost limiting. I am starting to think the wastegate must be opening up. I have had alot of people tell me a 10 LBS spring in the Turbosmart gate will tend to open at 6psi. I will know tomorrow if that is in fact what is happening. If it is then I am going to get a boost controler for it.
One thing is for sure, after today I have no doubt this thing will be a serious beast once i get all the bugs worked out of it.
While we were there I spoke with Turbo383WS6 about what was going on with my boost limiting. I am starting to think the wastegate must be opening up. I have had alot of people tell me a 10 LBS spring in the Turbosmart gate will tend to open at 6psi. I will know tomorrow if that is in fact what is happening. If it is then I am going to get a boost controler for it.
One thing is for sure, after today I have no doubt this thing will be a serious beast once i get all the bugs worked out of it.
OK, I disconected my wastegate sensing line and took it for a ride. The boost pressure shot over 12psi then I backed out. So I know it was infact the wastegate opening up, limiting my boost to 5.5 psi. It was also the large leaking sound I could heard. So the lag has been fixed and the limited boost has been figured out. Now I just need to figure out the spring combo in the wastegate to get me 15psi and start tuning it.
