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Discussion Starter · #21 ·
i got some p10 questions??

1) Do i need 444cc injectors if im running a GT28RS?

2) If my ECU is eprom'd and base mapped for 444 inj, can i still run stock 370cc if i run stock boost?

3) should i stop being lazy and run the AEM EMS w/ UEGO and tune out the injectors?


thanks!:eh:
If your ecu is tuned for 444cc then run 444. Depending on mods and boost and the amount of power you want to make will determine if they are big enough. A gt2860rs can easily make 350whp so you would need 4 bar fuel pressure or larger injectors
 

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Cross Member Bolt Holes Stripped

Charles helped me out a few days ago.

My question: So I stripped my crossmember bolt holes, what size should I tap it to so I can get some bolts back in there.

Snickers Answer: 1/2-13 (EG: 1/2" bolt with 13 threads per inch)

Result: Worked beautifully, Bolts grip better than ever and they are torqued back down to spec!

Thanks Snickers
 

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Discussion Starter · #28 ·
Why do they sell hot dogs in 10-packs and the buns in 8-packs?
Because they are smart and know how to make money

what causes exhaust rasp? Howto avoid it?
Turbulence, incorrect exhaust size, and poorly fabricated parts. Cheap formed collectors can increase and amplify rasp while full merge collectors shave a smooth transition and are much less turbulent.

The diameter of the exhaust pipe and DIA size and volume of the muffler will determine which frequencies are amplified and which are canceled out or "muffled"
 

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How does injector sizing work? Example: I have a det with a t25 and I put on 555cc injectors because I plan on upgrading my turbo. As long as I have an ecu programmed for 555cc injectors I should be OK. However how does the fuel delivery work? Do the 555 just use a lower duty cycle vs the 370cc? Is more fuel used or does it only spray what is needed to balance the mixture? So in essence both will spray the same amount since the turbo isnt looking for a lot of air?
 

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Discussion Starter · #31 ·
How does injector sizing work? Example: I have a det with a t25 and I put on 555cc injectors because I plan on upgrading my turbo. As long as I have an ecu programmed for 555cc injectors I should be OK. However how does the fuel delivery work? Do the 555 just use a lower duty cycle vs the 370cc? Is more fuel used or does it only spray what is needed to balance the mixture? So in essence both will spray the same amount since the turbo isnt looking for a lot of air?
Its pretty simple actually.

If you have say 80% duty on a 370cc injector at X rpm and Y load (say 6000rpm at 15psi boost) and you swap over to 740cc injectors, if you correct for the injector size your duty cycle will drop to 40%. this is because the 740cc injectors are 2x the size of the 370cc so to get the same fuel, A/F ratio for example, it takes less time with the injector open to spray the same amount of fuel.

basically always having more injector than needed is important.. but I do believe in matching the MAF with comparible injectors...

I.E. a Z32 MAF with 333 injectors is pointless as is 740cc injectors with a stock MAF

Why is there a choke on some headers? What does that thing do??
without getting over technical on header design and theory, the Header "choke point" on say a 4-1 does many things. Basically it helps maintain velocity of the exhaust gasses through the collector. the other half of this is if the choke is too big you can loose velocity through the collector and this will affect the pressure waves through the collector. on the other hand if its too small you can create too much backpressure and then have negative power results.

example,

I have seen a VE engine many times with a 2.25" choke make more power AND MORE TOP END POWER than a 2.375" choke. BUT when switching to bigger cams with more overlap, duration, valve open area, the results are backwards and the larger choke will make more power, and even more bottom end...

This is all the "basic simple explanation"
 

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Discussion Starter · #33 ·
Great thanks for the info.
One more question:

What's the best hybrid 5 speed trans for turbo?
Best is a bad word to use here... The 00+ trans are stronger and better for boost overall. While I think the P10 (or 99 P11) work well for boost, the 00+ is stronger even though the 00-02 P11 trans has a shorter 1st and 2nd gears. Might cause wheel spin easier but it wont break as easy.

00-02 P11 best
00-01 B15 with P11 Final drive

Or if you are not trying for over say 300whp then a 99 P11 will work great if you dont abuse it.

(my opinion)
 

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I have a header with 2.5 DP to mandrel bent 2.5 with a OEM muffler from a s13. I replaced my straight thru to cut down on noise, figured if I install one from something bigger than 2 liter motor it wont choke the flow as much. Was I right in that assumption?
 

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Discussion Starter · #38 ·
I have a header with 2.5 DP to mandrel bent 2.5 with a OEM muffler from a s13. I replaced my straight thru to cut down on noise, figured if I install one from something bigger than 2 liter motor it wont choke the flow as much. Was I right in that assumption?
Generally exhaust size is based on the total actual amount of air/gasses moving through the engine. I am not sure what size a OEM S13 muffler is, as in the inlet and outlet sizes. I know a few people use the Subie STI muffler because it is 60-65mm (which is close to 2.5" (63.5mm) and they keep it quiet. OEM mufflers are great because they are designed to remove a lot of noise. In using OEM mufflers for performance applications. I would try to find something slightly larger than what you are planning on using it on. mainly because the internal design will be restrictive to flow to disrupt the sound waves/flow path
 

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that's what i Did; ka24 is slightly larger than sr20. Maybe i can find a i35 muffler. I looked at WRX dual tip muffler but seemed too tall, it wouldn't fit right on the 11. I miss the nice growl but having a dead silent car is better. Just wondering if im wasting gas running JWT cams and choking the extra ponies, I rather have peace and quite then 5 extra HP.
 
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