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What Psi Boost


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#1 A1111j

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Posted 31 May 2022 - 09:37 AM

Hi just wondering what boost I should aim for. My compression ratio is going to be around 8:5 8:6 and I my aim is for 130bhp.
Thanks

#2 mini13

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Posted 31 May 2022 - 10:28 AM

engine spec? turbo? intercooler?

 

 

Assuming youve got a decent intercooler fitted, you can probably do that on around 8 psi, without your probably looking more toward 12psi.

 

with that compression ratio, you could run up to around 20psi ( pistons IAT's and setup permitting) , but youd need to be running a decent gearbox/diff/clutch

 

HOWEVER!!    I would start at around 5psi, checking everuything is operating as it should, ( ignition timing, and AFR, and slowly increase a few psi at a time.


Edited by mini13, 31 May 2022 - 10:30 AM.


#3 A1111j

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Posted 31 May 2022 - 10:50 AM

1293
I think its a T2 not 100% sure as I got it part of a kit with mirage manifold.
18cc forged pistons flush with the deck
21cc mse6 head
Running an intercooler asI have been advised to run one.

#4 mini13

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Posted 31 May 2022 - 11:56 AM

Ok, a t2 will probably run out of oomph about 160-170 hp, ideal for around 130hp though.



#5 A1111j

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Posted 31 May 2022 - 12:32 PM

I have a 7.5 psi turbo actuator would that be sufficient enough for 130bhp do you think?

#6 Ethel

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Posted 31 May 2022 - 01:31 PM

Yes, you can always bleed away some of the excess pressure to get higher boost.



#7 mini13

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Posted 31 May 2022 - 01:44 PM

yep, you can vary it a bit by adjusting the "preload", or add a bleed valve to up the boost significantly.



#8 Hpal

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Posted 04 August 2022 - 11:11 AM

Jumping on this topic. I'm planning my first turbo build. I think the gearbox will be the limiting factor on how many hp i go for, I've got a pre a+ rod change box as the DAM5626 ones which are apparently stronger are thin on the ground in Australia. Should/could i put 120/130hp through my pre a+ box? What can I do to help it take the power?

 

Current specs i'm thinking are:

1275 plus whatever overbore i need

minispares pistons

either new h beam rods or a+ rods

New a+ CAM 6232 crankshaft

MED st2 light flywheel and clutch balanced assembly

Minispares cross pin diff and 3.1 ratio

fusion fabs manifold for gt1752

intercooler

 

Compression ratio 8.6? Question, if i'm not squeezing 20psi into it and only going 130hp, should i be running CR a bit higher like 9:1?

If my gearbox can't take too much power should i be going for a gt1544 or something?

MED have advised that a st3 clutch might be suitable, but its a paddle clutch with a heavy spring, I really think it'll make it a pig to drive...

I'm new to this so just trying to get as much advice as possible.

 

Thanks all.



#9 DeadSquare

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Posted 04 August 2022 - 01:37 PM

The wonderful thing about a supercharged engine, is that after a few months, when the novelty wears off, you become relaxed and seldom see the full boost on the gauge.



#10 Ethel

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Posted 04 August 2022 - 04:17 PM

Guessing it's Pre-Verto if it's not  A+? 

 

Grey diaphragm isn't too bad, but I have a Metro master cylinder to push it. There was a Metty Turbo friction plate, a conventional disc without damper springs, but a good spec one should do.

 

The diff's the weakest link, go cross pin or atb. You may also be able to upgrade the layshaft. Otherwise just a god rebuild to minimum tolerances. Also, there's loads of shared thoughts on transfer gears to read on here.



#11 Hpal

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Posted 06 August 2022 - 11:26 AM

Yes everything is pre a+ as we didn’t get anything a+ in Australia. I have a cross pin diff to go in it, just wondering about the rest of the box (4 sync rod change) and it’ll handle the power or what I can do to strengthen it a bit. The cost of sourcing an a+ box is high due to shipping costs.




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