i made a post about the precision 6262 .84 asking if it is too small.

my setup is:
pineapple streetports
haltech PS1k
550 primaries, ID2000 secondaries
turblown divided manifold, older single wastegate style
tial MVR 44mm wastegate vented to atmosphere
11psi wastegate spring
3" downpipe and full 3" exhaust

well i dyno'd and tuned tonight, and when i started doing full pulls, i'd make it to about 6000rpms before the boost would shoot up to ~16psi and hit my boost cut.

anyway, it was at about 320whp at 11psi and 6000rpms.

i'll post a datalog for any of the haltech platinum guys. this run made it to 340whp before hitting the boost cut.

time to sell it for a 6766 or a s360. i'm now thinking a 1.00 or .96+ turbine housing?

 

Sounds about right for your setup. You'll probably enjoy a bigger turbine housing if your deciding to switch. Nonetheless 300whp rx7's are fun on the streets!
You'll be surprise how fast a 1.06 turbine spools on a stock ported 13b. Congrats on the dyno!

 

Why not correct the overboosting issue and see what the car can really do?

I absolutely would not move to something like a 6766 from what you have, that's a few steps up the chain and you won't be happy with the response IMO. Seems silly to just install another turbo before you know what the one you have can do

What are your power goals and planned boost settings?

 

rich, how do you propose i fix the overboosting issue without changing turbos? i'll be expecting a good response

my goal for this car is to road race with ~350whp and ~10-11psi and "good" response.

 

buy my s400sx FMW. 67.7 mm. i even have it listed on tennspeed. 1.10 t4 divided. $900 for you since your suggestions helped me on my starting problems

 

It sounds like your wastegate isn't sufficient enough. If it's running straight off the spring and still creeping like it is, 44mm isn't enough for ya. 16psi sounds like a good starting point though Just run low boost at that setting.

 

You will get the same problem on a 1:00 or 0.96 AR as well.

I was boost spiking to 28psi at 6000rpm with a Tial 44 on a 1:00. I went dual WG's and fixed the problem.

 

Choosing another turbo will get you in horsepower to psi you want ,but you have an issue and it would be ideal to upgrade to a 60mm wastegate.

 

A 44mm wastegate is sufficient if the manifold is routed properly. I wasn't the first and nobody can really claim to be, but I've had excellent results with dual wastegates for around 5 years now. It seems around 50% of companies are now offering dual wastegates standard.

Again, you should have no problem controlling boost with a single 44mm wastegate. Proper routing of the manifold is crucial for proper wastegate response. I still push dual wastegates as a standard turbo manifold option.

 

agreed with everyone else so far. stick with that turbo! are you using any AI? if not, fix that and turn the boost up a few more lbs when you correct the wastegate issue

 

You are running off the spring only correct, no boost controller involved/connected?

 

Given your goals you seem to have picked a good turbo, I'd stick with it.

Look into your boost controller line placement and go from there.

 

rich,
i'm running straight off the 11psi wastegate spring.

 

You might want to check you wastegate lines, check for tears or rips in it. Also check the diaphragm for tears. I had this same problem a couple of months ago with my Tial V44 wastegate, it was a combo of a ripped diaphragm and a clogged pressure source line that led to the wastegate. Once I fixed those two problems my boost control was rock solid. I'm running a 6766 @ 20psi on low and 25psi on high (plan on going higher, but my clutch doesn't like it right now). I'd personally stick with your 6262 if those are your power goals as well, should have awesome spool time and still deliver the power you want.

 

more boost? the 62mm precision should still be efficient at higher pressures where it should make much more then 300whp.

 

check the wastegate and ensure its not in any way damaged and it works. Also check the pressure/reference line for the WG. A 44mm should be enough

 

seandizzle, i had the wastegate opened up on my table about a week ago, checking the spring combination to make sure it was the 10.5psi combo before going out tuning. the diaphram was fine and everything was nice and clean and it good shape inside.

and let me rephrase the boost creep issue. the boost sits perfectly at 11psi from about 4000-6000rpms, then shoots up to my boost cut (16 psi) at 6500.

i am pretty sure the wastegate is functioning as well as it can.

 

Its an issue with wastegate or manifold as many have said. Nothing to do with the turbo.

 

It is not a wastegate, or turbo issue. It is a manifold issue. The wg runners are in the direction of flow, but there is a divider that runs up to the WG valve seat, blocking considerable surface area. The divider must be thick or it will blow out. This divider seperates the pulses completely before the valve opens which helps with boost response. That manifold was never intended for low boost, per the original owner's intentions.

Best solution would be to put in a 1.1 bar spring, and run it at 17psi. If that is not an option, next easiest solution would be a more restricitive exhaust system.

If one wants to run low boost you generally need our new manifold design.

 

What manifold is on the car?

 

the manifold is one of turblown's earlier single wastegate manifolds, which were designed for higher boost, apparently.


elliot, thanks for the reply. i do get the feeling though that the boost will continue to shoot to infinity though, and not level off at ~17psi...

do your new design manifolds have the same turbo flange location as the one i have?

(attached pic is from previous owner)

 

IF space allows it, why dont you cut the wastegate tubes off the primaries, and weld a wastegate flange on each exhaust runner? (where the wastegate tubes used to be)

 

The new dual wg manifolds are in the approximate same location, whether it's exact or not is hard to tell. I built that manifold you have now quite a long time ago I believe.


I highly doubt the boost pressure would go sky high as the engine is already past peak torque, and you have the smaller turbine a/r that will restrict the engine on the top end. You arent going to get more than another 1000rpms out of that a/r.

 

this is what i would do, you could probably get by with dual 38's

 

i'm thinking this is a perfectly good manifold for someone who wants to run higher boost, as it's very high quality and well made (as is everything elliot makes, apparently), so i could sell it to someone who wants to make more power.
i'd hate to hack it up.

but i need to run low boost for track days. my FD is supposed to be a weekend/track car, so i need to keep the boost/heat down, especially with this small turbine housing.