twin tuning/ drive pressure help

[mainer]

on my twins ihi over s475 with no external gate

finally got a bigger tune in... only been able to run up to about 70mph because of stock tranny and not wanting to go into 5th (slips in 5th)

its making about 38psi of boost and spikes to 56psi of drive pressure then holds about 50psi drive pressure.


question is... the big turbo is making 22psi of that 38psi of boost... so the ihi is only making 16 of that....


i think whats happening is its blowing the ihi gate open before its making much boost. would a ppe boost valve or manual boost controller help increase what the ihi is making?

i'm ok with the 50 ish psi of drive pressure if i was seeing total boost around 45....

i fully understand how the gates work with twins etc but this is my first time actually working with them. and hoping not to need a gate around the primary. as my s475 has the same hotside as trents s480 in his mpi twins and his setup does not have an external gate.

another option in the future is to pull the ihi out and machine the wastegate bigger. any one have a junk ihi around??

any ideas/ suggestions?

 

[diamondshocks]

you want the wategate to open as soon as it can to spool the large charger. holding the wastegate shut will just make it worse. as for machining it bigger. i port them out some on the modded IHI's i have been working on. it will ehlp to dump more air to the large charger

 

[IdahoRob]

You can't just add boost #'s, Compounding does not work that way.

 

[TrentNell]

you could try the boost valve but i think that might give you too much , i think nathan got rid of the boost regulated wastegates for a manual spring type like i have on my s300 not shure though . you are not that far off , if its feels fine i would leave it . i dont think you would see drive pressure decrease , might be able to squeeze bit more boost @ the same DP though . the big charger deff isnt needing a gate yet , and i experience alot of benifits from my waste gate porting i had done , now my gate is cranked as tight as it will go to level the boost between chargers , used to be oposite .

 

[TrentNell]

you want the wategate to open as soon as it can to spool the large charger. holding the wastegate shut will just make it worse. as for machining it bigger. i port them out some on the modded IHI's i have been working on. it will ehlp to dump more air to the large charger

i have saw a decrease in power by using that as a practice , i always heard that to be true as well but i have seen different in real life .

 

[diamondshocks]

i have saw a decrease in power by using that as a practice , i always heard that to be true as well but i have seen different in real life .

yes im only going by what i have read over and over but ill trust you here, haha, you have the twins. size of charger also can change it some though as well. VVT vs fixed, size of wheel both compressor and turbine along with the aggressiveness of the wheels

 

[TrentNell]

You can't just add boost #'s, Compounding does not work that way.

rob is 100% correct overall boost doesnt seem to change much.... just what chargers as induvidual make by themselves may vary . i was able to shave 5+ psi off total boost by gate increased flow on my little charger but thats because it wasnt enough flow to begin with and the larger charger's boost was low .

 

[racinmike77]

i have saw a decrease in power by using that as a practice , i always heard that to be true as well but i have seen different in real life .

You disagree when porting your gate helped you tremendously. Did i miss something? IMO a ported housing and ported wastegate on the top charger will help.

 

[diamondshocks]

You disagree when porting your gate helped you tremendously. Did i miss something? IMO a ported housing and ported wastegate on the top charger will help.

he waste taking about time when the wastegate opened, not porting it

 

[2500HeavyDuty]

a banks big head wastegate would probably help out alot since its adjustable and it flows alot more than stock

 

[mainer]

a banks big head wastegate would probably help out alot since its adjustable and it flows alot more than stock

how does it flow more than stock? its just an actuator....


also talking with dmaxvaz some we think part of my boost #'s being low is the stock converter/ transmission not loading it enough as I know my converter slips badly in 4th and 5th so not even sure if its able to lock up in the lower gears.

 

[TrentNell]

how does it flow more than stock? its just an actuator....


also talking with dmaxvaz some we think part of my boost #'s being low is the stock converter/ transmission not loading it enough as I know my converter slips badly in 4th and 5th so not even sure if its able to lock up in the lower gears.

hope you get it figured out . i def agree get the trans sorted out and go from there ...


one thing to note is that the trans can affect overall boost being low but will have no effect on the boost of the individual chargers . but i am shure you know that already

 

[RENODMAX]

The converter will definately help but how much of a fuel shot are you running?? If your not seeing the boost you want but cant romp on it because of the trans how hot of a tune can you really run anyway? Like trent said get the trans done and then see what you can get out of it.

 

[dmaxvaz]

The converter will definately help but how much of a fuel shot are you running?? If your not seeing the boost you want but cant romp on it because of the trans how hot of a tune can you really run anyway? Like trent said get the trans done and then see what you can get out of it.

he's workin on it, he is waiting on the converter to show up in a few days

 

[RENODMAX]

he's workin on it, he is waiting on the converter to show up in a few days

i know i supplied some parts for him