My Bad Boys are here (GTRS Turbo's)

[OZ GTR35]

Steve,

Turbine housing size is large, but I cant read Jap so the spec sheet does not help. See post 7 with a pic of the housing. Exhaust is a Jasma 3 1/2" with HKS dumps as per post 4.

Emre,

Yes I agree the result is no what I expected, I need cams and more air (3lt upgrade) to drive the turbo's, as I stated in the dyno results post.

We played with the adj cams heaps. 0,0 / +2,0 / +4,0 / +6,0 / +4,-2 / +4,-6 / +6,-4 / 0,-4 / 0,-6 and the best result was +6,-6 but there was not a huge difference once you got up in the + 4 or -4.

[Steve]

Well to give you an idea, I went from a 0.61 (1bar at approx 3000rpm) to 0.87 (1 bar at over 5000rpm) on a single HKS 3037. Having twin turbo, I would think the smaller the housing the better, as you have twice the volume of flow as a single - this would undoubtedly improve resonse.

When I fitted the 0.87 housing, tuning went a little way to improving response, but still no where near the 0.61 housing. If you are using 2 with large housings, it would be my guess that this is (a large) part of the problem, and perhaps look at getting a pair of the smallest housings you can find.

Another thing that doesnt seem right though is the peak power figure. At 1.3 bar, a 2530 will flow enough air to deliver 230rwkw on an RB20 or 25, grepins 2835 (of which the GTRS has the turbine specs) flow 275rwkw at 1.3 bar with a 0.68? (not sure, but it was the smallest one made for this turbo) turbine housing.

In tandem, I would have thought the combined flow of the GTRS would be much higher than 301rwkw, as it uses the 2835 compressor wheel. I cant remeber specific examples (anybody help out here?) but I was under the impression that even equiped with 2540s, a GTR would make better power than you currently have, with more response once the turbos finally (laggy) started making good boost.

The exhaust side, unfortuneately JASMA by itself doesnt tell too much of the story. I had a nismo jasma approved exhaust, dual resonator, and street legal. Unfortuneately, sound and power production go hand in hand. My car was choking, by going to a better flowing, straight through design, with smaller resonators, (and still JASMA approved) I also picked up boost around 300rpm earlier and the car feels alot more crisp off boost and on. It would be very simple to try unbolting the exhaust (from the cat, only 2 bolts) and running the car on the dyno again. Minimal cost, but it will also tell you alot about the performance of the exhaust sytem.

My current exhaust is the 3rd I have tried, the first one I had on was an N1 type, very straight, and a pretend resonator on the end - very loud, but the response and power were excellent. Just a tad loud for a daily driver:)

Stick with it, its pretty frustrating doing R&D on your own car (and expensive), but by the looks you have a couple of wrinkles to iron out and you should have a killer combination.

Good luck

EDIT, couldnt see the markings on the turbine cover in you picture unfortuneately.

[Sydneykid]

Hi Emre, from memory it is something like ...............

IT = inlet temperature

RT = reference temperature

RH = reference humidity

RP = reference pressure

TN = inertia setting

RR = ramp angle

PL = power loading

CK =check reference

Hi Paul, that dyno graph looks like what I would expect from a pair of 2835's. I have seen an SR20 with 1 X GTRS and compared it to 1 X 2835 and the result was the GTRS's built boost both earlier and faster. The max power looks OK though, so I am having trouble thinking of what the problem may be. It is a pity it stops at 7,200 rpm, I'd like to see what happens after that.

I have never seen any RB engine run +6 on the inlet cam, +1 or +2 is about it. But you obviously tried it on the dyno so no arguments there. Even -6 on the exhaust is more than the -4 we normally see, but not enough to worry about.

The only thing I can think of is the wastegates opening a bit early, the flattening of the boost ramp up to 5,200 rpm may well be a symptom of that. What rate wastegate actuator springs have they got in them? If my guess is right, I would say 0.7 bar? If that is the case, then I would go up to 1 bar actuators.

Next I would look at the ignition maps, if they are maybe a little retarded it will make a difference as to how fast the boost rises.

Have you ever done a leak down test? A lazy (but not dead) cylinder will slow down things at lower RPM and then as the rpm rises the effect is not so great. Maybe a good hour well spent.

That's about all the guesses I can make.

[OZ GTR35]

Syd,

Leak down tests, all pistons spot on.

Im using the APEXI boost kit, so Im not sure what the spring rate is.

Steve,

Changing the timing did not do much to the power curve, but it did develope knock at high RPM's so we did retard the car by a few Kw for safety but there was no huge gains when we started to play with the timing.

[meggala]

interesting stuff

[OZ GTR35]

Meggela,

Back to old school posts, where you talk about performance, argue over the best parts for our cars and bitch about power outputs!

[Sydneykid]

Hi Paul, the wastgate actuator rate should be stamped on the case of the actuator, you can usually see it from the top, on the front turbo.

The Apexi PFC boost controller kit uses a very good quality solenoid, but when you have a big difference between the initial opening psi of the wastegate actuator (0.7 bar or 10 psi) and the boost controller setting (in your case 20 psi), the solenoid has to work very hard to bypass this much pressure.

What we have found works well is to use a higher psi wastegate actuator (eg; go from 0.7 bar to 1.0 bar). This means the solenoid only has to bypass half as much ie; 15 psi to 20 psi. This removes any possibility of exhaust escaping past the wastegate under 1 bar (15 psi).

When you say "Changing the timing did not do much to the power curve"?

Is that changing individual points on the ignition map or rotating the CAS a few degrees?

What fuel are you using?

I'd like to get to the bottom of this, as I had a set of RS's in my mind for one of our cars, after the success we had with the single RS on the SR20.

[meggala]

yeah its really interestesting to me as I am fitting an trust t518z to my sr20 r32 soon and I was refered to this thread by some one seems like the charateristics of these turbos is extreme re driveabilty as we know the japs dont mind lag as they spend a good deal of time in traffic. I assumed they would be laggier as the ss's are more the 2510/30 replacement and the gtrs's the 2540r replacement still the figures are interesting may be raising the compression would help but I know you wont do that.

still as I said interestig stuff.

yes its is good to get back t the old scholl type threads

meggala

[OZ GTR35]

Sydney,

The GTRS are suppose to have a 1Bar wastegate actuator so the solenoid would not have to work as hard. The .7 bar boost setting on a 1 Bar waste gate is another mystery I have yet to solve.

Fuel BP ultimate no additives

Timing was changed using the Apexi menu (IGN/INJ, I think) that globally adjusts timing and duty. The Apexi timing maps are basically aggressive so as we advanced the knock increased.

Sydney Kid send me a PM with your number and I will call for a chat.

I too would like to understand the issue if it is not "The GTRS are too big for a standard GTR"

[Whoneedstherapy]

if someone wants to lend me a set in 3 weeks you can test it on a 3L with big cams

it doesn't suprise me they feel a bit big for an RB26. When compared to a 2530 and a 2540 they are alot closer to the 2540 in terms of outright response than the 2530. Even on an SR20 they behave alot closer to the 2540 than the 2530.

steve as for your theory about the exhaust housings, im pretty sure HKS dont make the GT-RS with many differently sized rear housings to mix and match from unlike there GT30 based turbo's.

[Emre]

AFAIK, GTRS was designed for the SR20 and than marketed for the GTR in twin form, surely the SR20 equvalent has a larger exhaust housing. Any chance of you having the SR20 ones OzGTR...?

For comparison, i am attaching my graph with 2530's running 1.4 bar.

3000 rpm = 75 kmh

4000 rpm = 105

5000 rpm = 135

6000 rpm = 165

7000 rpm = 195

8000 rpm = 215

If anyone wants to compare the data on the bottom of both dyno sheets, please go ahead.

My figures as i could make it are :

IT=29 degrees is the room temperature at the time (the probe was placed near the screen). My intake temperatures during the run was 44-45 degrees.

RT, RP and RH are the reference values as SydneyKid have put it, which i assume would be the values they had when they were calibrating the dyno or writing the software.

TN=3.5 - I believe this shows the mode used (shoot6, shoot4 or 8 etc) and is different value than Oz's .

RR=13 - Ramp rate 130 which can not be altered.

PL=1 - ???

CK=2 - ???

[Emre]

I have been corrected in my assumptions by Peter from Dyno Dynamics.

RT, RP and RH stand for room temperature, barometric pressure and humidity at the time of dyno session.

IT is supposed to reflect the inlet temperature and the inaccurate value will give a false reading. Placing the probe for a correct reading in turbo appliactions can be a problem.

The formula is :

Actual inlet temperature - IT value / 5 = x %

In my case : 44-29/5 = %3 can be added to the reading.

TN is the inertia setting relative to the power rating of the dyno. Dynos setup to accomodate more powerful cars may have larger rollers which will have a different inertia setting.

RR is the Ramp Rate and it's locked at 130 for Shoot 6 and 150 for Shoot 8 modes.

[OZ GTR35]

I have no doubt that the 2530 are a more suited turbo for a standard GTR then the GTRS's. I have bought the GTRS kit for the RB26DETT. The gaskets etc were for a 6 cylinder so Im sure it was not for the SR20. I spent some time on the web and I was unable to find any specs on the exhaust housing that was in English. I think the true test will be if Merlies GTSS do better then the 2530's.

Pitty your graph was not KW/RPM, this would allow us to identify the lag difference in the dyno runs.

[PurpleR32]

What I would like to know is why 25/30's made more rwkw power at 1.4bar than GT-RS turbos at 1.4bar.

Forgetting response, I have to believe there is something wrong when at the same boost, GT-RS make less power.....some 46rwkw less too!

I guess tuning is the key

[OZ GTR35]

Red,

It did not matter what timing /fuel/cam settings we used the car did not get any substantial increases. Cams in to the standard engine would help lots, but they don’t exist in my car so, tunning can only do so much.

[Sydneykid]

Hi OZ GTR97V, I see the 0.7 bar as being a problem I would like to resolve. If the GTRS's are supposed to come with 1 bar actuators, then 0.7 bar should, in theory, be impossible. The only explanation I have is that the boost sensor for the dyno is in a different place than the boost reading for the wastegate actuators. Is this possible? The alternative is that this pair of GTRS's came with 0.7 bar wastegate actuators.

The second question I would like resolved is the RT, RH and RP on the shootout mode. Both of the dyno graphs in this thread have;

RT = 25

RH = 60

RP = 101.3

Since one dyno room is in Sydney and the other is in Melbourne I would be amazed if the dyno room temperature, humidity and pressure were all identical, on different days a month apart, coincidence? I don't think so.

At least the inertia settings are different (3.5 versus 3.8), but hang on, why should they be? Both cars are 6 cylinder Skylines, aren't they? Why would you need to have different inertia settings?

Is it time for a separate thread on Shoot Out Mode?

[OZ GTR35]

On my way home tonight I will set the apexi to .7 bar and I will check what the max boost was when I get home. This will hopefully close the .7 issue.

[OZ GTR35]

Well, I spent some time at EC last Monday, I did a about 10 min at .7 bar setting, the apexi showed I only boosted to 0.71 Bar, Fu#k knows how but the car did drop in power and .7 was registered. I need to get a boost gauge and slowly pressurise the wastegate and watch when what PSI it opens. I will attempt to rig something up over the next week or so. This should identify the point of 1Bar actuators.

[jezzrrr]

My Dyno Graphs are in. I made a mistake, the peak was 300 not 310

Out of interest OzGTR97V have you made any advances on the power/response you got out of your GTRS's since you last posted ?

[OZ GTR35]

No, I dont think you can do much with physic's. I have a R34 VSpecII coming in from Jap, should be here in the next month. I am not waisting time or money on the R33. I will probably for R34 N1's on the R34.