I totally get that, I was just thinking about the wg being affected thats all.

 

if you stay on the gas how much boost do you get in third 4th or 5th gear?

could you just not be spooling the turbo enough yet? you say the boost goes up from 3-5 when you go from 1st to 2nd....

it could be your turbo isnt spooling up yet

 

no I'm pretty sure it is. When I look in my datalog I can see a sharp slope where it spools up and a peak when the wastegate kicks in. Then it slowly goes down by a couple of tenths every half second or so. Its definatly not rock solid at a given psi once it is up to boost.

I do want to say that third gear does get a little higher boost. But it won't make boost under 3-4k or so. So doing this in 4th or 5th gear is a little dangerous around here.

 

my friends rx-7 has a turbo that is a little too big for it ad it doesnt make peak boost unless you stay on it until halfway through 4th gear, it really sucks below that

 

I put the boost reference in one of the ports on the TB that goes to behind the blades. This should be close enough to directly off the intake to see if the TB is causing a boost drop. The boost is the same. I did notice though that the turbo seems to be spooling up sooner.

I guess I'll just have to crank the spring down and call it good. I really don't know why I'm not seeing more boost. But, I guess it'll have to do for now.


Could it be the overlap in the cam? I've always been told that a larger overlap will bleed off boost. If it really is leaking boost could I be flowing a bunch of cfm out the exhaust? making the 350ci use as much air as a 400ci? I guess without any kind of maf I wouldn't know the exact amount of air.

 

Have you verified the spring? It wouldnt be the first time I have heard of wategates coming with the wrong spring.


I doubt it. The turbo wants to spool to 40psi if it can (you get my point) ...the wastegate shouldnt be opening till it reaches the spring psi... I dont think cam has anything to do with IMO. I'd double check the spring.

 

Double checked the spring, and just to be sure I got a new black spring from turbonetics and the same exact thing happened.

 

hmm....time to think some more....

 

Nope. With a turbo, the opposite happens anyway. Boost pressure is almost always higher than boost. So, any bleeding that occurs is boost into the intake port.

Mike

 

I wouldn't worry about it, why not just spend 5$ and make a boost controller?
In my limited experience, my wastegates have always worked to within 1psi of advertised, but that is limited, and quite frankly suprising to me. The only issue I have currenlty is mine has small(less than 1psi), but rapid fluctuations at full boost (on the order of 200kp/sec). This kicks in my acceleration enrichment if I use mapdot. I have tried two different styles of boost controllers (both manual, one a home-made ball and spring, the other a 20$ bleader style).

 

For now I'm going to just deal with it. I tightened down the spring tensioner in the wastegate and I think I'm seeing around 6psi now, no datalog yet. I can definately feel a pick up of horsepower.

I'm just worried that there is something wrong with the turbo setup that I'm missing. And if it is causing boost to not be where it should and not keeping it rock steady afterwords something might happen to the engine, or worse yet the turbo.

Mike, I do agree that the back pressure pre turbo will be much higher than the intake pressure, but when you take into account the velocities of the air I still think there is some kind of bleed off going on there. I guess there's no real way to prove it asside from swapping cams, and even then its not 100%.

 

It is not your cam. Depending on the Intake/Exhaust pressure ratios, the cam might make less than optimum power at certain points, but it will not affect the boost the wastegate ends up allowing. This may have came up already, but have you checked everything for boost leaks? Are you sure the sealing ring on the external gate is installed properly and seated? These things will also make boost response slow in general. If this has already came up in this thread, then I apologize for not reading the whole thing. If everything is alright, don't worry about it, just turn it up with a controller if necessary.

 

Well, here's an update for you guys. I took it to the track yesterday and once the sun set the stock clutch seemed to hold alright. At about 6 psi I managed to get a 12.5 @ 117 with a 2.09 60'. Not bad going through the stock mufflers. Earlier this summer the car went 13.1 @ 109 n/a but that was in TX, much lower elevation. I think there is a little more in it since I was shifting around 6k and not closer to 6500 like I should have been, and I'm not sure about the tune at all.

So now that I have kind of a benchmark I've got the engine pulled and and switching to my 383 with the McLeod clutch setup. No more clutch slip for me

 

way to go man.. smooth wrenching!

Chris

 

12.5 at 117 thats very fast

not a bad run

what do you think you will run with a good clutch