Max boost without detonation

[rbsileighty]

I was wondering if anyone has explored the max boost on a RB20 on US 92-93 octane. This is with stock compression. My trim level of my T3/T4 is going to need some boost to make power and I wanted to know how high I could go without detonation.

I'm not to worried about fuel. I've tested the stock injectors and they will become ~293cc's when fuel pressure is raised to 3.5bar. My fuel system consists of the SARD Racing FPR, MKIV fuel pump w/ rewire (to 8 gauge wire), and an S-AFC to dial things in a bit.

Let me know, those who have explored the boost limits, what you think is safe to run.

[boost_boy]

At most 15psi, but even then you have to take into account ambient temperatures and a few other variables.

Dee

[rbsileighty]

I was just logging in to say I have a Hybrid FMIC as well... so that should bring down discharge temps. The one heat range colder plugs also might help pull some heat out... we'll see I guess.

[boost_boy]

I would throw some octane booster in there just to be safe. It does work!

Dee

[accel junky]

Is the 15psi a general rule no matter the turbo trim? Shouldn't horsepower be used for the limit?

[Sil240]

I have a magazine from AustraliaAnd they put either 550's or GTR 440's(with resistor pack) in autronic ecu and a TD06-20G and they made 450 Wheel horsepower on STOCK InternalsThey maxed out the stock injectors somewhere along the line ill break out the mag and find out where

[boost_boy]

The T3/T4 turbocharger will definitely max out the stock injectors at or around 10-13psi boost. But with the fuel additives, you can keep the detonation.

Dee

[Imissmyturbo]

Not all T3/T4's will flow enought to max out the stock injectors. I bet if you would take a .48 AR exhaust with a stage I wheel and a 46 trim compressor you would max the turbo out first. Also boost pressure has less to do with detonation then other factors. Timing, A/F, intake temp, and spark plug heat range will effect detonation more then boost pressure.

[rbsileighty]

My trim level is small (not sure since it was second hand), and the turbine is a .48 a/r which is why I'm going to need boost to pull some power out of it.

The comp map of a 46trim T04E is showing it's maxed out 42.5lbs/min out to 60% EFF when running ~18psi . Granted this is far out of optimal eff... but the flow at 7800 w/ 18psi out of the RB20 is ~33lbs/min which is in the 74% EFF circle (with the .48a/r it might be out in the 60% range again).

I have a scramble button on my Profec B, so that's what I was thinking I might set it to if it doesn't start detonating out there. With the 46 map @ 7800rpm w/ 12psi I should be putting out 27lbs/min (72% eff)... so that might be my normal boost range.

These boost levels are all inside the 50 trim T04E, but I really have no idea what the compressor side is on this turbo (what happens when you are pressed for time in purchasing... wouldn't have bought this one if I had thought more about it). It is a turbonetics polished housing with no numbers on it.

Does anyone have specs of the different ones? What is the diameter of the inlet on a 50 and a 46 trim? I have seen a few VW combos that are for the 1.8 (this one was bought originally for a honda) that are running a .48 turbine w/ a 50 trim, so I'm hoping since it's a turbonetics turbo and maybe for some B18... I'm dealing with the same. I know this one is bigger than the Saab T3 inlet we have laying around.

How do the 2L 4G63 EVO VIII's pull 19psi with a 8.8CR if we can only run 15?

[Sil240]

Umm im not sure about Evo's but eclipse turbos had 440cc injectors stock and everything in there is forged

[rbsileighty]

Based on that theory... 440*4=1760cc vs. 270*6=1620cc so if I ran ~294cc+ (stock injectors w/ 3.5bar fuel pressure) injectors I'd be ok. Forged internals shouldn't affect detonation (survivability maybe), and I think WD (correct me if I'm wrong) was running higher boost, with alcohol, than 19psi on the stock hypereutectic pistons.

Seems like the best thing for me to do is take it to the dyno and find out for myself (carefully of course)...

Thank you all for your help!

[Sil240]

Why dont you just buy rx7 injectors???i believe there 550's and they plug right inCheck out megalla.com (not correct spelling)

[rbsileighty]

550's are a little to big for what I'm doing right now. I'd like to run higher pressure to possibly help fuel atomization anyway...

[DSMs_Suck]

4g63's dont have forged internals anyways

maybe a forged crank... but thats it. def. cast pistons/rods