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Discussion Starter #1
My R33 GT-R V-Spec feels very slow at low rpm (about 1-4k), and I'm trying to figure out why.

It has stock exhaust, stock filter box (with Apexi panel filter), PFC , PFC boost kit, stock injectors, stock turbos, 100mm FMIC. Running 1.25 bar boost.

I know it's not exactly optimal with stock exhaust, these are the mods the car came with from Japan.

I had a few runs on the dyno a little while ago, this is the result: 285 hp at the hubs (4WD)



With these mods the car looses in a drag with my friends R32 GT-R with only FBU. It's impossible (without kicking the clutch) to make the tires slip on a very wet road in first gear. What do you guys think?
 

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Discussion Starter #2
Also, the stock 444cc injectors touched 98% duty cycle at one point! Isn't there a rule of thumb saying that 1cc = 1 hp or 444cc = 444 hp at 80% duty cycle on RB26?
 

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You do actually get used to the power after a while and it will seem slow.....then you just want more more more :chuckle::chuckle:
 

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Between 1 and 4,000rpm a ni-on(?) standard R33 doesnt feel that quick to me either lol....

How long have you been running stock turbo's at 1.25 bar ? And to think I was a little bit wary of turning them up to 1 bar !
 

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Discussion Starter #7
I had an experienced mapper take a look at the map while on the dyno, he said it was fine, but added a bit more fuel in some cells.

I forgot to mention that it's a N1 engine, which means it has metal turbine wheels. 1.25 bar should be fine, right?

Geordieboy: I'm not used to it, it's been like this from day one. But you're right, we alway want more. :D
 

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285 hp at the hubs is about right for a near standard gtr ..approx 380 give or take 10 hp at the flywheel
my bet is you could be losing response low down because of the big intercooler you have fitted ....also the standard exhaust will be strangling it ..
 

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you're killing the car on both ends with the intake and exhaust. With an open pipe exhaust and pod intakes, you should be seeing close to 400bhp without any other mods.

Upgrading the intercooler on stock turbos is a mistake - all you are doing is creating a big pressure drop and lag creator in your intake.
 

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Discussion Starter #10
Thanks guys, I didn't even think of the intercooler. The previous owner fitted a lot of Tommy Kaira parts, among them the 100mm TK intercooler. I'll get rid of it and replace it with a stock one.

I know the exhaust is a limiting factor in my setup, I was just trying to figure out why my car was so slow and less responsive compared to my friends stock R32.

Any ideas on what could be causing the "wobble" in the red run on the torque graph from 4800-5500 rpm?
 

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I don't see keeping the bigger intercooler as a bad move, especially when it might be easier to bring other parts up to spec (eg exhaust) for relatively little outlay.

I'm running stock R34 turbos on mine and it's incredibly responsive with an Apexi GT intercooler, which has a core of approx 600 x 210 x 130mm.

As far as pressure drop is concerned, if anything a bigger intercooler would be better, surely? I presume your concern is that there's an extra volume of air for the turbos to pump before the pressure will start to rise. While that is undoubtedly true, how much of a percentage increase in volume do you think the 100mm intercooler would add to the entire inlet tract from turbos to throttle bodies?
 

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stock ceramic turbos spool faster than steel NI turbos..sort your exhaust and intakes and there should be a significant difference in both power,torque and responce.

Also if i were you i would turn the boost down.Its quite high for stock fueling
 

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+1, I had stock ceramics up at that boost. They lasted a month before I melted all six pistons. The turbos made really good doorstops after that.
 

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Discussion Starter #14
kingsley: I have to get hold of a stock intercooler anyway to be able to register the car, it has to be 100% stock. This way I'll find out just how much a larger intercooler means for the engine response. I might keep the larger one for later.
It's a complicated subject, I have some books about designing intercoolers and piping which probably has the answers about pressure drop.


creedonsr20det: Do you now how much faster the ceramics spool compared to the N1s?
I have ordered the Apexi Power Intake kit and I have new elbows and downpipe for the exhaust, just need to find a good catback. I turned down the boost immediately when I found out how high the duty cycle was, need to order larger injectors and a upgraded fuel pump.

kistmetcapitan: Why? Did you do it by accident? "Everybody" knows the stock ceramics shouldn't be run at more than 1.1 bar.
 
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