3.0 16V engine mods, etc

[Thom]

Here you go - GTX3584RS with a peak compressor flow of around 85 lbs/min and a peak turbine flow of 27.5 lbs/min with a 0.82 A/R housing.

GTX3584RS_Comp.jpg (82.45 KiB) Viewed 1219 times

GTX3584RS_Turb.jpg (81.57 KiB) Viewed 1219 times

GTX3584RS_MB.jpg (205.74 KiB) Viewed 1219 times

As previously this is with pushing the boost as high as possible to get close to the peak compressor flow yet have plots that follow each other more or less realistically in the compressor map. The resulting figures are a bit ridiculous - 700 lbs.ft at 5000 rpm and 800 hp at 7000 rpm. The back pressure to boost ratio at 7000 rpm is 46.7/31 = 1.5.
To reduce these figures we can lower peak boost from 35 to 28 psi :

GTX3584RS_MB_28psi.jpg (208.75 KiB) Viewed 1219 times

600 lbs.ft between 5000 and 6000 rpm, and 750 hp at 7000 rpm but the back pressure to boost ratio at 7000 rpm is still at 42.1/28 = 1.5. This is a huge amount of torque and we can certainly question its relevance, as according to the matchbot this is also what I get at 4000 rpm with the GTX3576R, and I certainly do not think this is the case in reality.
Rather than wondering about the accuracy of values it is perhaps more relevant to consider how they evolve in between engine speed points.
With the GTX3584RS we get somewhat of a plateau of torque from 4000 to 7000 rpm with power peaking at 7000 rpm.
With the GTX3576R the plateau is between 4000 and 5000 then an almost linear drop, though not severe even if it stalls at 6300 rpm with more than 23 psi.

For what this is all worth anyway, as I really cannot believe that exhaust manifold pressure can be any lower than boost pressure up to 5000 rpm. Also the maximum turbine efficiency mentioned on the turbine map most certainly applies to the largest housing.

[333pg333]

With the CR and cam specs you mentioned it sounds to me there may be room for quite a bit more than 20 psi... feels a bit odd to me to suggest now pushing it a little after suggesting in the past a conservative approach in view to your recurring misfortune... Trust your tuner is the bottom line, but if the sleeves end up moving I'll be glad to send you a set of used S2 studs of unknown mileage for real cheap... lol...

I'd also be a bit wary of revving such a long stroke engine that high with our typically big and heavy pistons, if the specs are still as in the email you sent me 4 years ago. I'd keep the boost down the higher the rpm...

I guess you are still turbo shopping for asking about the G40-900?

Oh, yes totally Thom. The conservative approach is valid and real. My inquisitiveness is the only thing driving me towards upping the boost on the dyno to see what a few more psi will gain us. The race engineer who works on this car and crews at the track (plus runs his own race team in the support series to the Oz V8's) suggested we actually think about pushing it to the point where we see headlift on the dyno. Yes, that will be the end of the session but we'll know what our limits are should we require them at the track. I suspect that won't happen but based on Gustaf and Rod's experiences, they both went to 28+ psi on similar motors and didn't get headlift. Gustaf clearly experienced other issues and Rod had oil pressure problems iirc. Again, my intention would be not going to such high boost. And in all reality we will probably just stick to the 16psi as before. The engine specs are essentially the same as you've seen. Obviously significantly lighter components than OEM but we won't be revving to the 8800rpm the builder supposedly designed it for.

No, not turbo shopping. Just curious and interested in your motor and the calculations you've displayed.

[Thom]

I can't remember how much torque Gustaf's engine made on the dyno before he ended up breaking the girdle, was it around 950 N.m / 700 lbs.ft?

ETA : just found the dyno sheet and it was the block that broke. 966 N.m is not too bad.

[Thom]

One thing I have probably learned so far playing with this match bot is that it is not possible to predict exactly how a turbo will perform on any given engine... but didn't we all know that already?
The match bot is about assuming which peak boost pressure a sampled engine will handle without grenading itself within its dynamic compression ratio and an ignition timing map with a "reasonable" shape, and if the engine can support the resulting torque at peak RPM from the air flow provided by a turbo running not too close from the edges of its compressor map... then great, Bob is your uncle. All the rest such as spool, back pressure and the driving dynamics resulting from the reciprocating behaviour between the cold and hot side is for anyone to find out, as apart assuming that a "high" back pressure to boost ratio at peak RPM should mean good spool down low, it al feels like being blind in a dark room and finding something that might be there or not.

[chris white]

Did this last year and works great it was a speedforce eBay purchase used and while I first cut the bumper bar for in front of box frame I ended up cutting the box frame since it’s a full race car and mounted to protect from front bumps and bruises as it’s a endurance racecar.

2.5 16 valve turbo motor and makes 300ish hp

looking at the pic you will have a problem (i had it too!). the top plate of the intercooler and the bumper structure eliminate any air flow to the top half of the radiator. so the coolant passing though the upper half gets no temp drop - overheats at the track very easily.

[Thom]

Perfect weather this morning for a bit of tuning. I have adjusted the boost to 23 psi (260 kPa) again and get spikes to 290 kPa (27 psi) at 4800 rpm. Here is some logged data, with an ambient temp of 22°C.

240413.jpg (149.98 KiB) Viewed 1143 times

100 to 150 kph takes ~2.3s but 100 to 200 kph is not measurable as flooring the throttle after changing to 4th causes the rear to break loose, and what I had thought was the compressor running out of flow seems to be more of a mix between a loss of traction and the OS Giken LSD's remarkably progressive and smooth action that helps keeping the car (about) straight. It seems the LSD needed all that performance to finally show its true value, and at a boost level of 23 psi there is clearly enough compressor flow left above 6300 rpm where the match bot suggested the compressor would not keep up. The injector duty cycle suggests the 1200cc injectors are maxed out.

It is a lot of fun and now just below scary or perhaps I am just getting to grips with it. With improved boost control it should be close to perfect but at this stage with how hard the boost hits it is a bit of a "rough diamond". I have never loved that car so much in the 18 years I have had it.

[Boostfeen]

Hey Chris thanks for the tip what did you end up doing to get airflow back up to the upper radiator? Better custom ducting with some more of the 951 bumper cut open? We are running a custom front splitter that gives us plenty of high pressure on the frontal surface and several large exhaust vents in the hood. Actually about half the hood to be honest ha

[Thom]

When I had the SFR stage 2 intercooler I reused the ducting for the factory IC and added some ducting to force air onto the upper area of the radiator. It worked well.

[Thom]

Back from the dyno... 517 hp / 529 lbs.ft (718 N.m) @23 psi.

240420_Dyno_SS.jpg (157.8 KiB) Viewed 1031 times

(First run was at 20 psi (1.4 bar) of boost, the other two at 23 psi (1.6 bar). On the very first test runs the engine was overboosting to 30 psi which triggered the MAP limit so had to adjust on the fly the boost table to clear things up, whence that first "clean" run at 20 psi)

240420_Dyno_log.jpg (148.52 KiB) Viewed 1031 times

The tuner said I should redo the harness to the fuel pump as the power should be much higher than that with such high injector duty cycle values with 1200cc injectors. He also reckoned that the 0.82 A/R turbine housing was too small for a 3L engine. The loss of power above 6000 rpm as shown on the spreadsheet is not anywhere near as obvious on the road, though back pressure may be climbing fairly steadily above 6000 rpm.

The bottom line to me however is the plateau of torque of more than 370 lbs.ft (500 N.m) from ~3200 to ~6500 rpm which I hope illustrates a bit better what I meant about this set up being really good on the road.

[Bergerac]

The tuner said I should redo the harness to the fuel pump as the power should be much higher than that with such high injector duty cycle values with 1200cc injectors.

I'm curious what pump you're running and what wiring you have now? I'm a little concerned I've underdone my harness as well. Are you measuring your fuel pressure at all? I would have though 1200cc would have been plenty.