goodspeed

someone in the TID thread, said that with a boost controller, you cannot lower boost???? why can't you? Is this true or not, If I have a full exhaust , intake and tid, i will be well over 10 probably closed to 15 psi on spikes. If I got a boost controller, I couldnt tune it to never go past say 10 psi???? why not......

tIIforever

I think what they might have been talking about is that you can't lower to boost below what the turbo puts out from the factory like you can't set it to 4.5 on an 88 because the factory has it at 5.5 but you can have it so it will go to 10 and hold it there

goodspeed

ok, thanks, i think i just misunderstood what was said.. I was pretty sure you could set the boost at a certain point. The person said that the boost couldnt be lowered any more than the system puts out..meaning if im getting spikes or 8 psi, now, I couldnt get a boost controller and lower to 8 so it doesnt spike to 10psi or whatever...

that would of ruined my whole plan, I didn't really want to buy bigger injectors, more computer crap. I just want full exhaust, intake and tid, with a boost controller set at 10psi and a super afc to tune it around, and I should be safe...

Chris Ng

Here's what I ment about not being able to lower you boost with a controller...

Stock boost is let's say 7 psi.. this is controlled by your wastegate.. when you hit 7 psi (well actually your wastegate starts to open sooner then 7 psi) your wastegate opens to vent excess boost into the exhaust.. however the reason you start to creep/spike/boost past 7 psi when yous tart adding intake and exhaust components is that you have now increased the ammount of flow.. your wastegate still opens at 7 psi, however the wastegate can nolonger vent enough of the increased boost pressure.. you have overcome the wastegate...
all a boost controller does is allows boost pressure to increase beyond the set point of your wastegate actuator .. once you hit the set point, it vents the pressure back through your wastegate..

Therefore, if you are flowing enough to boost to 10 psi without a boost controller, a boost controller will NOT lower your boost below that of 10 psi.. you can however use it to raise your boost to 11 psi and beyond..

If you want to lower boost or keep it from going out of control without a boost controller, your'e going to have to port your wastegate or getyourself an external wastegate, or go back to stock components..

Scott 89t2

nope you can't lower it. a good ball and spring controller with really short vac lines will probably help stop creep though. so it might lower it a bit. but you certainly can't control it.

Josepi

So what's one to do? Ported wastegate? New aftermarket wastegate? More turbo newbie q's

goodspeed

i want to run a full exhaust, intake, tid, my boost is going to be way over 10 psi probably?

whats the best step in controlling it??? i want to just have 10psi with a full exhaust, intake, tid....

rx7_turbo2

I have 2.5" RB downpipe and presilencer, and the N1 dual catback, as well as the TID mod, my crappy Autometer gauge says I am running between 7-8psi, that feels about right but I need to verify the gauge to be sure. I would also like to run about 10psi and will use a ball and spring boost contoler to do so.

Chris Ng

Full RB exhaust (3" downpipe, 3" midpipe, presilencer, ypipe, mufflers), TID mod, HKS filter .. without any sort of boost controller on a stock turbo this gave me 11 psi boost, sometimes creeping to 12-13 on cool nights boosting in 4th and 5th gear.. porting the wastegate brought boost down to 7psi max.. I then made use of a boost controller to raise boost to what I wanted (knowing that the wastegate could bleed enough boost off now to keep me from creeping or spiking)

I have a feeling that we need to confirm the accuracy of rx7_turbo2's boost guage to make sure it's accurate..

There is nothing you can really do to control boost pressures if you're already overcoming the stock wastegate.. you can port the wastegate, but you can only port it so much.. (really a mute point since you can safely port it to deal with boost pressures of about 12 psi.. anything beyond that and you're going to start worrying about turbo efficiency anyways).. or you can spend alot of money and get an external wastegate.. which is also useless for the stock turbo..

My suggestion? port your stock wastegate (its a pain in the *** to remove the turbo, but you['ll be learning more about your car at the same time).. If you dont' want to do that right now, save your money for the basic items you'll need to run higher then normal boost.. FCD, Fuel Pump, Injectors, S-AFC in that order..

There are a bunch of people in the group that we have running higher then stock pressures with stock components right now and havn't blown up their motors.. however I'm sure it's in the back of their minds as to how long it can last.. even if the motor seems to be handling the boost and your car is faster, you're always going to be worried .. you want your motor to make lots of power, or to make lots of safe power?

unfortunately with performance there is always a tradeoff.. and that tradeoff usually hits you in the wallet.. but you can't get something for nothing..

At very least, if you are going to run higher boost, you're going to need an FCD and I would suggest a S-afc as well.... I use the s-afc to tune down my bigger injectors from running my car rich all the time, however I have had success in using the s-afc in tuning the stock injectors with a rewired stock fuelpump to make things a bit richer to keep you relativly safe.. The one thing you have to watch out for doing that though is maxing out your stock injectors.. you really don't want to have them lock up on you (injectors arn't cheap).. 85% duty is concidered the upper limit of running your injectors safe.. at 10psi I have seen the primary injectors hit over 87% before the secondaries cut in.. at that point I've seen max duty of injectors (primary and secondary fireing) of close to 80% without any correction with an s-afc.. now imagine what your duty would be like when you use the s-afc to richen your mixture up to compensate your boost..you have a very small window to work with...

Scott 89t2

how are you measuring your injector duty?

Chris Ng

Scott: My AVC-R has injector duty reading..