you must have missed the part where I said that this was my spare engine and that I've got a low compression stroker sitting in the garage for when I have all the bugs worked out of the turbo setup. No need to blow up an expensive motor if I don't have to.

But while I'm driving this engine around I migh as well get the most out of it. Which is why I want to know how much more timig I should be able to add with it still being safe, or as safe as these things ever are. From what I've seen people are running 6-8 psi on stock engines with 26 degrees of timing. Does this sound about right for a stock engine?? If so I've got about 10 more degrees I can put in it.

I am planning on upping the boost, but the problem is I have a racegate with a black spring that should be good for 9-13 psi and I'm seeing 4-7 on my datalog. Turbonetics is sending me a new spring and hopefully that will fix it.

 

Yep, getting rid of those stock mufflers will decrease spool time, increase power, and reduce the tendancy to detonate.

Be careful, though, because boost will increase possibly alot.

 

How will removing the mufflers make boost increase??

I'm still up in the air about doing the mufflers. I really like the quiet ride and my neighbors really do too. If I do decide to do it that would be another winter project.

 

By removing backpressure across the turbine, the dP (differential pressure) across the turbine increases, thus spinning it to a higher rpm.

When I removed my Hooker 3.5" Aerochamber, I gained 8 (yes, eight) psi boost.

 

Right, but the wastegate is in there to prevent that. And its reference is from the intake tubing so it shouldn't effect it.

I guess if it was restrictive enough it would cause a higher back pressure in the post turbo piping which would cause a higher pressure in the pre turbo piping and the extra force might cause the wastegate to open sooner.

 

nice setup BUT a sloppy install..

 

I wasn't insinuating to do what I do (that would blow some head gaskets for sure)

I was simply trying to point out a trend, and that you could run considerably more than you are currently. What kind of engine management are you running? If you have knock sensing/retard just increase a degree at a time and watch. If not increase and listen carefully, let off the second it rattles or bye-bye head gasket. Good luck with it, and I will keep my comments to myself from now on.

 

So what do you think I should have done differently to make it cleaner??



I8AStang,
I did end up taking your advice and moving the timing up. I did a 2 degree/psi drop until 4 and then a 1 degree/psi to 8. I am running an Accel DFI Gen 7 for tuning, but I don't have the knock module stuff. I'm actually not running any kind of knock module right now. That's why I'm very cautious about moving up the timing. I would do it by sounds, but I'm not very good at picking up these things, especially with all the road noise that is there.

 

How does it feel with the extra timing? Also, one thing to keep in mind is do your tuning in a tall gear. In 1rst and 2nd I can run 3 degrees more timing than I can in 4th. Things also don't happen as fast and tend to be a little more quiet.

 

I ran it through first and second quickly on my way back from lunch. It feels a little stronger, but not a huge amount stronger. I'll have to go and find a big back stretch of road to try out third.

 

Tell that to my 2 blown head gaskets and boost-referenced wastegate . . .

Lots of people report a change in boost when adding or removing a muffler, though most are in the 2 - 3 psi range. The wastegate is an open-loop controller, not feedback. You set it up to run a certain amount of boost, but if any variables in the system change, then the boost level can change also.

You would not have this problem if you use an electronic boost controller becuase it is a closed-loop PID controller.

 

Mike, I've been thinking about this for a while and I think I have it figured out. If you just look at the forces on the wastegate you have these forces that are keeping it closed The back pressure from the down pipe and the spring in the wastegate, and these pressures pushing it open, the boost in the intake and the pressure in the headers. When you take out the mufflers it would seem that the main change would be the back pressure in the DP would go down and cause the wastegate to open quicker.

So now here's the key that I think I finally figured out. The turbo is propelled by the pressure drop across the turbine. So basically with the same exhaust engergy the turbo will spin faster due to the greater pressure drop.

And with this happening the wastegate would have to open further to keep the same boost levels, but that doesn't happen so the boost ends up going higher until the wastegate opens.

Is this about right, or is there something else that I'm missing?



Ok, next question. I was making 7 psi of boost on my 383 with a 224/218 cam, and now with the same wastegate setup I'm making 4 psi with a 350 and a 230/236 cam. Could this be from the mufflers that I'm running on it now, or is it from the greater overlap in the cam or both?

I know with supercharger guys if you drop psi on a setup you'll be running more hp usually(exhaust or head change). But with turbos I'm not sure that applies.

 

Sounds good to me.

What mufflers were you running then?

 

congrats on actually taing the car for a ride...

im in the same boat i keep geting more and more into dept trying to get my turbo setup running

 

Open down pipe for the engine dyno.



cndctrdj,

Thanks man, hang in there, its well worth it when its done