-7/9s Or -5s Garretts

[NXTIME]

Agreed, Paul. I have always been of the belief that the HKS turbo ratings were very conservative and have used their 'offical' power rating as the ATW figure guide as to what can be achieved. My old turbo's (HKS GT 2835's - rated at 400hp each) made 546rwhp@16psi on initial tune and are of similar specs to the Garrett 2871's.

As for the GTSS's....have a look at what figures are achieved on the blacktop dyno. Flat-11's high 10's are possible.

[shy_s6]

so whats ppl's recommendations to make 320-340rwkw @ around 18psi (Reliable), my engine previously made 370awkw with hks turbo set up when it was in its original 33, has big ports cams ect

[GTR1993]

need -5 for 340 at that lower boost.

[donkey]

hey

i just made 320AWKW on 18lbs, full boost at 3800 (of the top of my head) -5's, custom dumps, inlet, pump, injectors, G4 LINK, std cams, std engine etc, HKS twin light weight fly wheel, asked tuner to do a safe tune, lots of torque 850ft lbs......

got quite bad shuffle though......

robbie

[Bakes]

Here is a graph showing GTSS vs -5. This was done on the same car and on the same dyno.

http://4.bp.blogspot.com/_vhpEGyEVhes/SDya...00-h/GDZIL4.jpg

the -5 were 500 rpm behind the GTSS up until ~4600rpm where they draw level but at 5500rpm the -5 pull ahead of the GTSS.

At the end of the day, make your own choice. Here is a couple of good threads for you to check out. Take note of the guys that had GTSS set ups and moved to -5 set ups, they say they prefer the -5s. It depends on what you are after.

I bought a set of -5s

http://www.gtr.co.uk/forum/99765-gt-ss-gt2530.html

http://www.gtr.co.uk/forum/96210-5s-7s.html

[Swiper the Fox]

Here is a graph showing GTSS vs -5. This was done on the same car and on the same dyno.

http://4.bp.blogspot.com/_vhpEGyEVhes/SDya...00-h/GDZIL4.jpg

the -5 were 500 rpm behind the GTSS up until ~4600rpm where they draw level but at 5500rpm the -5 pull ahead of the GTSS.

At the end of the day, make your own choice. Here is a couple of good threads for you to check out. Take note of the guys that had GTSS set ups and moved to -5 set ups, they say they prefer the -5s. It depends on what you are after.

I bought a set of -5s

http://www.gtr.co.uk/forum/99765-gt-ss-gt2530.html

http://www.gtr.co.uk/forum/96210-5s-7s.html

that is to be totally expected...the -5's are supposed 2530 equivalents...id like to see if -7's would pull ahead of them...i think not.

My car made 460+ awkw on BP98 with 20psi and backed it up the next day with 450+ at autosalon...it made 355awkw on 11psi...thats nuts! That is BP98 yes just your STD bowser fuel...The best was 504awkw at 25psi with Sunoco fuel.

Our Superlap car has a HKS TO4Z it pulls 450+kw at 24psi...with one of my tunes in it (read...not the best tuner lol)

People waste money on parts they dont need just for the sake of 'having them' then whinge when they say HKS is too dear. MAX PSI is going through this now as he is wondering why his -10's are not even in the same sport as my GT-RS's.

My new drag set-up runs a modified HKS T51R SPL BB...its going to be responsive too...just watch this space.

HKS FTW...its the only turbo i will use.

Edited January 28, 2009 by DiRTgarage

[Bakes]

Sweet Dirt, just dont forget that you will be installing my immitation HKS Garrett turbos though

[Swiper the Fox]

Sweet Dirt, just dont forget that you will be installing my immitation HKS Garrett turbos though

Hey there is nothing wrong with the Garrett's but the HKS items seem to work better. On a street car with lower boost levels the Garrett items will work very well.

Bakes ive got some old HKS boxes here ill get you to bring the Garrett's around in them...hehe

Edited January 28, 2009 by DiRTgarage

[Waza_GTR]

I got 408kW at the wheels with -5's on 95 octane no problems. Just need to put a bit of advance on the intake cams and they come on real early.

[DSTROY]

I made 316rwkw on 18psi using -5's on a internally stock motor with only basic mods, full boost comes on at about 4500-5000rpm its a good rush, but when revving out first when you hit second you have to wait for the revs to pick up before it starts pulling again.

[PHA71L]

i got my 5s on yesterday car is not tuned yet....

and is running 14psi pulls harder up top all ready than the stockers but it is a fair bit more laggy!

dose not really come on to about 5000rpm but im sure with a tune it will drop again alot more...

and i also do not have adj cam gears....

but with a tune and more boost i bet its going to pull really hard!

they also sound alot better than the stockers

[djr81]

If im doing it right, which is highly likely i am not... being its the first time ive tried it all & im not getting all the variables exactly right (VE. BSFC, peak torque RPM etc etc)...

I just used a rough estimate going off what the doco said, and the notepad im using is now 3 pages long with numbers

But... if by some stroke i was near enough to correct then 550hp (the figure i picked) with a 12:1 AFR... it is certainly able to be done by both turbos, running over 20psi of course, which is what ive seen as per the comp map.

Albeit its right near the top, but still within the boundaries none the less. The -7s are at the limit, -9's similar but bit more room to move around.

How does two turbos affect things though, i guess you half it as two turbos flow air

If not, then my calcs are definately up the shitter somewhere, and i wouldnt be surprised if that was the case

Perhaps you could enlighten on some of the things for a more accurate result for people? (VE, BSFC etc)

Ill redo the numbers again, but i think the guide might have a typo too

The important thing to note is this:

As a very general rule, turbocharged gasoline engines will generate 9.5-10.5 horsepower (as measured at the flywheel) for each lb/min of airflow. So, an engine with a target peak horsepower of 400 Hp will require 36-44 lb/min of airflow to achieve that target. This is just a rough first approximation to help narrow the turbo selection options.

Say we use 440rwhp & 22psi from a -9.

So, for the sake of the argument we have a -9 running 440rwhp. Now you need to convert this to flywheel horsepower. So add 1/3 (Say). You get 586hp. Divide by 10, then again by two (2 turbos) & the airflow is 29lb/min per turbo.

As for the pressure ratio you have 14.7 (atmosphere) + 22 (boost) / 14.7 (input pressure) = 2.5.

I usually round these up a bit because the input of the turbo does not see atmospheric pressure as there are losses across the filter element and because the MAP sensor is away from the turbo itself. Say 2.8 for the sake of an argument.

This can be plotted on the -9 compressor graph.

What does it tell you?

Well the point is way up in the top right hand corner of the map. The efficiency is falling away and generally the turbo is struggling as evidenced by a shaft speed of approx 150,000rpm. The problem with running here is the lower efficiency of the compressor means more heat is pumped into the air which increases the pressure drop through the intercooler which inturn means a higher pressure ratio is needed to flow the same mass of air. This is why you see a relatively large hike in lbs boost for a relatively small return in rwhp.

If you plot the same point on a -5 compressor map you get a much different result. My R32 runs 435rwhp on 14.7 lbs. plotting this on the map shows if anything the -5 is larger than it has to be at these outputs.

Anyway the point is despite the fact that these figures are all approximate they are far more illuminating than HKS numbers of a 300hp turbo or whatever they happen to be quoting.

As an aside if you can graph the airflow meter voltages versus the engine output you can plot the whole of the engine full throttle run on the compressor maps. Attached is Nissans airflow meter mass flow versus voltage graph. This can also be done using the MAP sensor to calculate the PR. It is easy to do once you have correlated engine output in rwhp to airflow in lb/min. Saves mucking about with many of the Garrett calcs.

Edited January 28, 2009 by djr81

[Lithium]

Thats very interesting, I opened the maps and its as you say - the -9s are really falling over up there by comparison to the -5s, which prior to first finding a compressor map for them I would have expected. I am SURE I have seen a map for what was listed as "GT2560Rs" which were ~60mm exducer and was a bit more like a bridge between the -7s and the -5s.

Either way, the -9s still look a fair bit better than the -7s haha

[R31Nismoid]

Well of course they are falling over, they are at the limits

But fact of the matter is they can do it, which is the point compared to "WA" regardless of the rubbish about not even 300rwkw on page1

[djr81]

Well of course they are falling over, they are at the limits

But fact of the matter is they can do it, which is the point compared to "WA" regardless of the rubbish about not even 300rwkw on page1

Please understand that in WA fighting the good fight (pick your side) in the TUNER WARS is far more important than anything else car related.

That they can do it is one thing. That you may want them to do it is another. What I was trying to point out was the problem with a higher PR from the turbo is alot more heat pumped into the compressed air. You get a triple wammy - more heat because of more compression, more heat because of a less efficient compression & more heat again because the turbine neads a higher PR to make all this happen. Now the intercooler can take out only so much heat.

But yeah I am continually surprised how far some people are happy to push their turbos. I can't say I have any real feel to working with turbos at the limits (or past them) of the compressor maps (as opposed to the compressor itself). I do tend to think that because of the approximations you have to make to find the operating point on the map mean you lose precision & therefore have to rely on the realworld for verification. Which leaves you exposed to being mugged by reality.

Anyway I would grab the -9's in preference to the -7's. And probably the -5's in preference to both. But that is just me.

[Adz2332]

Ok after hearing all this im leaning towards the 5s as im reali after the kick in the pants feel...

[djr81]

Ok after hearing all this im leaning towards the 5s as im reali after the kick in the pants feel...

If you grab the -5's get some cam gears to go with them & spend the money for the dyno time to get the response down low.

This is less of an issue with the -9's.

A good set up wont give you a kick in the pants. It should have a soft transition when it comes on boost.

[R33GTRKid]

Ash, the point is the tuners over here are not willing to run the turbos on the limits of their capabilities and risk blowing shit up!

Hence why I said 300 to 330 RWKW from GTSS's is pushing too much and asking for trouble, thus I would go the -5's if I wanted 300 plus RWKW.

At the end of the day, what you are saying is stupid and akin to me saying, yes my RB26 can rev to 10,000 rpm, but for how long!

[Johnny]

I wish all gtr drivers had access to different turbo setups to feel how they are on the street; honestly ive got a big headache after reading all the information provided by the members.

I jst wanna add something i read about HKS n garrett; that a garrett turbo must never outperform a HKS turbo from the same type e.g. 2530 and -5

I love the point about pushing the turbo to its limits; im chasing only 250-270awkw and although the stockers will do that, i dont want them running at full puff: kinda like "the candle that burn twice as bright, burns for half as long"

anyways im hanging out for Bakes results from his -5's and ill definitely post my results from the -7's ill probably wind up getting.

[PHA71L]

well im lined up for a tune next friday with my 5s so ill post what it makes ill only be using stock afm tho for now....