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What turbos is this gtr running

vspecv

By vspecv,
in Engines & Forced Induction

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vspecv Proficient

vspecv

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I feel light headed, i need to sit down :D  

It makes that sort of power with that sort of response, at a little over 1.5bar. Im no expert but that is brilliant. Do you happen to know what cams and compression ratio the car is running... std stroke and no special fuel?

I notice that most dyno pritnouts with big numbers are usually concave curves, and doing the math, you get more urge if you reach the same number with a convex curve....

compression is standard i beleive, hks pistons.

cams hks step 2, 280/10.20mm

mobil synergy 8000 fuel

standard 2.6 stroke.

could prolly be improved with smaller cams around 260, but has a nice lumpy idle :wassup:

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Merli Grand Master

Merli

Posted
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bah what, u want that dyno sheet aswell or should i take a photo of the guage :D  

mild port job

:wave: Nah dude, I believe you 100%... You don't strike me as the kind of person who would lie like that.

My point was that the airflow from that "23psi" would have been a LOT greater than on a standard engine... 280 degree cams, ported and polished head... That reduces the head restriction a LOT over a standard engine, so if you were to make the same power with the same turbo setup on a stock engine, it would require a lot more "boost pressure"...

My "bah" was mainly aimed at Roy's surprise that it was only using 23psi :wave: You have to take into account head work and big cams before being amazed at such a low boost pressure :(

Roy Grand Master

Roy

Posted
Posted
My "bah" was mainly aimed at Roy's surprise that it was only using 23psi :D You have to take into account head work and big cams before being amazed at such a low boost pressure :wave:

Even with head work and cams, thats not a lot of boost considering how its making its power.

I would have though a turbo that can provide 250rwkws at 4250rpm (good power for that rpm in my book) to have to run a lot of boost to march past 400rwkws

Even with cams/headwork etc, the inertia of turbines and compressor is what it is, and for a turbo to spin that well at moderate rpm, i would have assumed it wasnt that big a turbo, hence would need plenty of boost to make the sort of airflow for over 400rwkws....but it seems im wrong...since its got forgies stop playing games and give it 1.8bar :wave:

Merli Grand Master

Merli

Posted
Posted
Even with head work and cams, thats not a lot of boost considering how its making its power.  

I would have though a turbo that can provide 250rwkws at 4250rpm (good power for that rpm in my book) to have to run a lot of boost to march past 400rwkws

Even with cams/headwork etc, the inertia of turbines and compressor is what it is, and for a turbo to spin that well at moderate rpm, i would have assumed it wasnt that big a turbo, hence would need plenty of boost to make the sort of airflow for over 400rwkws....but it seems im wrong...since its got forgies stop playing games and give it 1.8bar ;)

I don't think you're quite getting the effect of headwork and 280 degree camshafts though :P

At the risk of treating you like a n00b (which obviously I know you're not), you have to remember that boost is just a measure of head restriction, NOT airflow.

Lets say that particular turbo kit needed to push 1200CFM of air through the motor to hit 417rwkw....

So if you strapped that entire turbo kit and accessories onto a stock motor, you will need to push 1200CFM of air through the engine to make the required power. This might equate to a 40psi (arbitrary value) head restriction to make that power.

But because this engine has had work to reduce the head restriction (and therefore improve the airflow through it), although the turbo is still pushing 1200CFM of air through the motor, you're only measuring a 23psi head restriction (commonly called "boost")...

"hence would need plenty of boost to make the sort of airflow for over 400rwkws...."

That doesn't really make sense... boost has nothing to do with airflow... It has everything to do with head restriction... You can have eleventy billion CFM of airflow and 1psi of "boost" if your head is good enough :)

Sorry if that's bleedingly obvious to you, I just wanted to make sure we're all on the same page here :)

Roy Grand Master

Roy

Posted
Posted

Yeh i understand what you are saying, my prob is i dont articulate myslef very well. :P

Even with cams/headwork etc, the inertia of turbines and compressor is what it is, and for a turbo to spin that well at moderate rpm, i would have assumed it wasnt that big a turbo....

Im using the term boost when i should probably be saying shaft speed. And for you to have sufficient shaft speed to generate enough airflow to make 250rwkws at 4250rpm, i would have thought the turbo has reasonably small wheels, meaning lower inertia and quicker accelerating turbo.

So my thinking was smaller the wheel the less cfm per revolution (ok it has a lot to with no. of blades, pitches of wheels etc etc). So i would have thought that to make 250rwks at 4250rpm then the compressor wheel is already got a few rpm on board, relativley small so not capable of providing huge amounts of airflow. The fact that it made another 170rwkws i would have thought the wheel speed would be thru the roof to flow that sort of extra cfm.

Is that making any more sense, wheel speed and boost are often thrown around with the same general meaning...typically higher wheel speed more cfm and subsequent boost as you are trying to squeese all those molecules into the same volume of space.

Merli Grand Master

Merli

Posted
Posted

Yeah, I understand what you're saying :) It's all Sydneykid's fault, he picked on us in another thread for misusing the term boost, and I've carried it over into this thread :P

And yeah, that is a very convex curve for a peak figure of 417rwkw... I'm also impressed ;)

vspecv Proficient

vspecv

Posted
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u guys are making my brain hurt.

to be honest, i probably am a bit of a noob when it comes to all the technical stuff and to be honest , i dont have the time nor the interest.

Find somebody competant who has the knowledge and who has done the r&d and use there expertise, most on here would know ben and prolly have heard of the garrets he uses, he has the big daddy on his r33 and leewah has the son of and i have the sister of.

i put my faith in him, as i know he will always steer me in the right direction, i do all the spanner work, but leave the brain work to others

we wanted to crank a bit more boost in, but detonation started to rear its ugly head and since this car will spend some time at the track, safe tune was paramount.

NRB Rising Star

NRB

Posted
Posted

Don't you mean the $5 a night slave does the spanner work? :P I think it's a very impressive graph and final figure Dean. I guess you'll be blasting past me when I (eventually) get out on the track again; it's been over 12 months.

I had a small chat to Ben about increased sump capacity, baffling and spun bearings today... a lot of the problems have stemmed from incorrect oil choice in the guys who've done the damage.

Sydneykid Grand Master

Sydneykid

Posted
Posted
It's all Sydneykid's fault, he picked on us in another thread for misusing the term boost, and I've carried it over into this thread

Oh yeah, it's always my fault:Paranoid:, go right ahead and put shyte on the guy who is simply trying to educate the unwashed. :bonk:

Even if they don't want to be educated :talk2hand

Roy Grand Master

Roy

Posted
Posted
to be honest, i probably am a bit of a noob when it comes to all the technical stuff and to be honest , i dont have the time nor the interest.

Find somebody competant who has the knowledge and who has done the r&d and use there expertise, most on here would know ben and prolly have heard of the garrets he uses ...

LOL sadly i cant afford such a toy so i have to enjoy just the nuts and bolts aspects of cars. :P , which thankfully i do.

"Ben" as in Race Pace?... apparantly he doesnt touch RB20s even if your a paying customer... it would be interesting to see him try and come up with a good Garret combo for a tweaked RB20, as obviously he has the RB25/26/30 recipe right.

Merli Grand Master

Merli

Posted
Posted
Don't you mean the $5 a night slave does the spanner work? :rofl: I think it's a very impressive graph and final figure Dean. I guess you'll be blasting past me when I (eventually) get out on the track again; it's been over 12 months.

I had a small chat to Ben about increased sump capacity, baffling and spun bearings today... a lot of the problems have stemmed from incorrect oil choice in the guys who've done  the damage.

Ooooh... interesting! ;)

Care to share what you learn't about oil choices with us? x.gif

vspecv Proficient

vspecv

Posted
  • Author
Posted
Don't you mean the $5 a night slave does the spanner work? :rofl: I think it's a very impressive graph and final figure Dean. I guess you'll be blasting past me when I (eventually) get out on the track again; it's been over 12 months.

I had a small chat to Ben about increased sump capacity, baffling and spun bearings today... a lot of the problems have stemmed from incorrect oil choice in the guys who've done  the damage.

are u serious, i will prolly have 3 more gtrs and a few porsches by the time u get to the track

Sydneykid Grand Master

Sydneykid

Posted
Posted
I had a small chat to Ben about increased sump capacity, baffling and spun bearings today... a lot of the problems have stemmed from incorrect oil choice in the guys who've done  the damage.

Sorry I personally don't agree, I have yet to see one single case of damaged bearings in a GTR as a result of the oil itself failing. They have all been oil surge and resulting starvation caused. I don't care what oil you use, if you don't baffle the sump and go on a circuit, you are at RISK. :D

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