JET951

t3rra, Maybe try at a lower RPM so that you are on boost, or even as was the case with us run it flat our from low speed through the gears.
Sean

Paulyy

Isn't it more accurate using rpm to work out speed by using gear ratios and tyre sizes? That's what i'm using.

I also do it all in 3rd year i just let it roll at 2000 rpm on a huge stretch of road and let it rev to limiter.

t3rra

Will do and record in the same way

5sec run would suggest a power off 380/400 hp based on 1350kg curb weight

Pualy would be some round 500hp

Would my hot side be holding me back? Iv got 0.82 housing to try but if is not rolling off the boost then would it make any positive increase

Given Paulys results his turbo must be on boost by 60mph, with less boost I would say gtx3076 would be the better turbo between them as we're unable to utilise the high boost safely

Don't get me wrong gtx3071 is still a good upgrade over stock as spool hasn't been traded, but it seem 76 don't spool much later. Wonder with the boost kept at 21psi if 3076 would work with 0.63 hotside

Paulyy

500 rwhp? no chance. Tonight i'll go out and record + log a run. i'll use my go pro to get the speedo readout.

I should be close to 400rwhp.

I'd like to see your car on a roll from 1500 rpm to see when your boost comes on. But you'll increase power with a .82 housing. You should have amazing response with your set up now.

t3rra

I'm quote figures at the fly not rear wheels.

Would sort off off increase do you think I would see? Been told by a few EVO guys that smaller housing is fine until u see it choking the turbo and dropping boost vs rpm increase larger housing will produce gains but higher then the boost I'm running

Response wise it's slower then 26/8
like the build from cruze to full boost in the power range

From 1bar the 26/8 would increase 0.1 bar every 50 rpm where the gtx seems to be more every 100/150 rpm

So all thou 1 bar is at the same rpm 1.4 is 200/300 rpm later

Anywhere below 2500 rpm will light gas will hear the turbo wishtle

Don't want to take this thread to far off track.

JET951

Not at all Pauly, GPS are meant to be quite accurate, probably mores then your means of measurement. The problem you will have will be with tyre sizes, not only does every manufacturer have different rolling diameter within a specific range(for example 245/40/17 toyo will not have the same rolling diameter as a yokohama 245/40/17) not only that but even the same brand and model tyre have slight variations. Added to that tyre wear, even 1-2mm can make a significant difference and finally tyre deflection when accelerating.

Sean

Paulyy

Post here

https://rennlist.com/forums/944-turb...ga-thread.html

I don't think it should play a lot really? i was playing with a tyre calculator looking for tyre sized for my new wheels and and with some sizes i was seeing around 5km/h difference. I mean going up from a 245 45 16 to a 245 50 16. it changes 3km/h so to speak.

JET951

Yes thats my point of not being as accurate. Going from the manufactures original spec back in the day, the outside diameter of the tire could have been close to the specific setting of 627mm OD but then we take into account that not everyone doing this test may have the same tyre. Some may be 628mm or 629mm OD or possible more, or it could go the other way and be smaller. then we addd the deflection on the tyre during acceleration and it could be out by more them 5kph. Thats getting up to 8% i think of the 100-160kph time. correct me if I'm wrong as I'm doing the calculations quickly.

So from the digging around i have done most GPS performance systems run between 5-10hz. 5hz being 5 sample rates per second and 10hz being 10 samples per second. And as far as i can gather the 10hz mode is accurate to within 0.02 from the 100-160 kph range. Disclaimer is that it was read on the internet which we all know is made up of crap.

Paulyy

you're not wrong. like with anything though. There's going to be some inaccuracy tolerance somewhere.

JET951

Yes of course. I forgot to mention wheel spin too. I may have to change back over to the slicks for the performance test as i do get slip in third gear. For my street wheels i just use street tires, continental DW's 255/40/17's. They are much nicer to commute to work with.

333pg333

Just leave the slicks on all the time. Man up!

I think that as your lap times are very close to the time from the official transponder, then your acceleration times will be pretty close to the mark as well. Even if they’re 10% out (which I doubt) you still have a VERY fast car. Did the times seem to correspond between Eastern Creek and Wakefield Park? I know that the corner leading onto the straights are different.

Thom

Sean, 3rd is now very slightly shorter than with the 944T gearbox, but not enough to affect the way the engine gets loaded.
Well agreed about the shape of the powerband, and now I am just making do with a hotside/camshaft combination that is not quite allowing the engine to peak out at higher rpm but which makes it very easy to drive... so much that I am working on shifting the powerband to the right a bit. I probably can further shave one or two tenths off but I don't expect to get below 3s with that turbo/camshaft combination.

333pg333

I'm hoping to get some data from my car. Be interested to know how it accelerates on the same patch of track as Sean's. The other thing which Sean touched on is the slicks. My guess is that they help get the car out of the hole really quickly. Even faster than our Medium R specs. So perhaps that's worth a few 10ths too? With our new turbo and 1.5 bar, I was having to feather the throttle a little bit out of the corners leading onto the straights last weekend.

V2Rocket

60-100mph..3rd gear 951 box...

12 seconds

t3rra

My logger does have a timer records 10/1 sec.

With 285/30/18 I made my tire diameter 24.7" now I was recording a log before I put larger cone filter on not for a glory run and stopped at 6200 =98mph 3800 =40
20 degs intake temp
29 at 6200 4.3 secs

In 3rd I'm getting 0.8 bar 3125 49mph starting from 2360 37mph

5.5 secs from 49/98

Didn't make 1.4 bar till 4100 but was on 1.2 3500

Give some idea off gtx3071 0.63