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Discussion Starter · #1 ·
i was thinkin about this today, why does the APC cut the boost way back once you get over 4,000rpm? i mean, you have a whole nother 2k of RPMs to work with, why not boost them? is it like, dangerous or bad for the engine or something?
 

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mike in your particular situation it's likely due to lack of fuel, lack of charge cooling, and increasing cylinder temps... my apc doesn't cut back till after 6k... but I have a huge FMIC, bigger injectors, RRFPR, and a 2.1 head.... all make a difference, it's likely lean, and pinging, you just can't hear it... the apc deals with the situation before you can hear it
 

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Discussion Starter · #3 ·
Breakin5speeds said:
mike in your particular situation it's likely due to lack of fuel, lack of charge cooling, and increasing cylinder temps... my apc doesn't cut back till after 6k... but I have a huge FMIC, bigger injectors, RRFPR, and a 2.1 head.... all make a difference, it's likely lean, and pinging, you just can't hear it... the apc deals with the situation before you can hear it
ah, that would do it :lol: i'm working on it though... slowly now, soon i'll have rent on top of other monthly payments, so progress on Uma is gonna get even slower :cry:
 

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My '89 felt like it was boosting through the entire RPM band the last time I drove it. Looked that way too from the boost gauge as it didn't drop like it had all the previous times. Now it's "discontinued" so I can fix a bunch of stuff, so I haven't even started it in a few weeks.

Could only go by feel...I'd wack the tach and it'd flip out...then go back to dead. Seemed fixed the last time I ran it but I didn't go anywhere that time.
 

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So umm you hit full boost at what 3500rpm? And then you get cut back at 4000rpm? That must suck, atlest NA cars have pretty uniform power delivery through the whole rev range.

Well the 4000rpm powerband is gooooodness in my c900.
 

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Discussion Starter · #7 ·
well my APC was stock... i unplugged my wastegate a while back, and it boosted GREAT all the way up to redline, and i've only heard it knock once :confused: my APC, when hooked up, always cuts the boost down past 4,000rpm to early to mid yellow
 

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****** said:
So umm you hit full boost at what 3500rpm? And then you get cut back at 4000rpm? That must suck, atlest NA cars have pretty uniform power delivery through the whole rev range.

Well the 4000rpm powerband is gooooodness in my c900.
No the NA cars have a increasing power delivery with r/min. If you look at the power curve it basically shoots straight up from zero to ~125 at redline.

The turbo cars hit max power at 3000 and then are basically flat to the redline. They don't hit a wall you have nice even power. But because of this even when I am "hammering" the car I usually upshift around 4000 (until I am in 5th then I go all the way ;))
 

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900t said:
No the NA cars have a increasing power delivery with r/min. If you look at the power curve it basically shoots straight up from zero to ~125 at redline.

The turbo cars hit max power at 3000 and then are basically flat to the redline. They don't hit a wall you have nice even power. But because of this even when I am "hammering" the car I usually upshift around 4000 (until I am in 5th then I go all the way ;))
I meant uniform as in uniformly increasing power delivery unlike turbos which have nothing untill they spool up.
 
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