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Discussion Starter · #1 ·
i did alot of searching a/r ratings, but i couldnt find an awnser.

i have a .63a/r ex and .50a/r comp turbo. just making sure my logic is correct, i only want low boost like 8-10 psi, and my motor is an h23 so im hoping the non-ideal sized turbo wont be so bad, seeing as how i have a rather large displacement motor.

my questions are:

will the .50 a/r compressor side hold 10ish psi on a h23?

and will the bigger exhaust a/r benefit me in anyway? or will it only make it spool slower? will it spin faster overall sorta like gearing?

and most of all, i have a .48 a/r exhaust .42 a/r comp saab t3 turbo, can i use just the exhaust wheel and housing off of this with my new center section and comp side? i know you can do it with the compressor side but is the exhaust housing the same way?? i want to keep my brand new centersection cuz i duno how the saab's seals are.

and that leads me to, the new one i have is only oil cooled, and the saab is oil and water cooled, can i use the seals, bearings and comp housing off my new one, or should i just put the saab exhaust hosing on the new center/comp?

any help MUCH appreicated, plz dont flame i searched, these are prelude specific questions. all iv found is my .42 comp is way to small. nothing about a .50 comp, or bigger exhaust then comp info.
 

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Well, first off the a/r is just a ratio. You need a compressor wheel that flows the correct amount of air in the correct area for your setup and that is determined by reading compressor maps. You use specifics off your motor and turbo to see how compatible they will be in your application.

That brings me to my next point. One of the most important aspects of deciding which turbo is its application. ie midrange, low-end, or top end Different turbos would be used in each situation. So, that would be very helpful.

Honestly, on a 2.3L motor, I would not use anything smaller than a .63a/r turbine because it has enough displacement to keep spool quick, but it is large enough that needs to be big enough to breathe. As in, it needs a larger wheel and housing to expell exhaust gases.

With a larger turbine a/r (.82/.90/1.00, etc) you will sacrifice spool time, but make more power because the turbine will flow much better and typically a larger compressor is utilized, so more air will be forced in.

In conclusion, I would us a .63a/r turbine .50a/r t3 super 60 for a basic street 10psi on a H23. If you are looking for better output and dont mind losing a couple hundred rpm of spool a 50trim t3/t04e .63a/r turbine will allow the capability to approach 300+hp if desired.
 

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x2 to what GC said above.
to add to it, the .48 a/r exhaust housing is extremely small for an h23. you'd spool practically off idle, and would have a very large restriction for higher rpm power, and if you mated it to a larger compressor side it would for sure cause compressor surge which damages the turbo.
so no, it would not a be a good idea to use the .48 a/r turbine
 

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Discussion Starter · #4 ·
so my .63exh and .50 comp is actually pritty ideal for what i want? i guess i didnt make a bad choice after all. and in the future all i would have to do is get like a .60 or so a/r comp to see over 300?
 

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i have an .63ar on my GT35. is that going to be good enough for 450-500whp? i assume that an .82ar would be better. I do more street/daily driving tho
 

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Discussion Starter · #6 ·
i whould think it would be fine as long as you are using a external wastegate, as not all of the exhaust will need to go threw the turbine
 

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yeah ive got one. problem actually happens when my wastegate gets overloaded and my boost creeps like hell. Lovefabs ramhorn design flows almost too well
 

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Discussion Starter · #8 ·
time for a bigger gate or some better piping that merges into the dp under the motor. ideal is atleast 18 inches from the turbo for the merge. you can also try flarin the wg pipe out to a bigger diam right after the wg to try and avoid getting a bigger gate.
 

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something everyone in here is forgetting is that the a/r of either housing has little to do with anything if the actual wheel sizes are unknown.
the a/r basically just is a measurement of the taper inside the housing. for exhaust housings:
lower a/r number = more taper = higher velocity = faster sooner spool but more restrictive
higher a/r = less taper = lower velocity = slower later spool but less restrictive

a/r on compressor housings really has little to no effect on anything.

for compressors, the actual wheel class is the biggest concern. second to that is the trim of the wheel.
for exhaust side, its a combination of wheel class, wheel trim, and housing a/r. the combination of it all, not one single thing in itsself

for example, a .48 a/r 76 trim t4 exhaust wheel will flow similar to a stg 1 t3 .82 a/r 56 trim exhaust
 
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