I was wondering if there is a general rule on how much psi you gain with nitrous..say 75shot. Anyone who has used a 75 shot know how much boost creep to expect?

If you have a good wastegate it might not creep. If it does, try setting initial boost lower.

 

Well I was talking about on the 14b. I was talking to Aslan and he said that he set boost on the Laser to 10psi and it would creep to 20psi.

 

Maybe this is too advanced

 

Maybe this is too advanced

It's nearly impossible to guesstimate what a certain motor would do given a certain variable.

 

Well I was talking about on the 14b. I was talking to Aslan and he said that he set boost on the Laser to 10psi and it would creep to 20psi.

I think I would just go with Aslan on this one...

-Dan

 

I think I would just go with Aslan on this one...

-Dan

I'd love to know how Aslan set the boost to 10psi. What is his wastegate spring?

 

Im having a problem like that too...i set my boost at 10Psi...it will creep up to 17psi on 1st gear and on 3rd it will creep easy to 22 psi and hit fuel cut...checked the actuator...it works fine...it opens up..would this be my exz manifold leaking thus giving low boost levels at low rpms..and at high rpms ganing more air flow spinning the turbine to crazy levels....i was thinking if i put my boost controoller on my friends car..using the same setting as i had...what level the boost would be? Its a Hallman ES....Please i dont know wha is up with thiss thing...and im sorry that this might look newbyish...but nobody would respond me...i have a 3 inch turbo back too....and a wastegate dump tube...on the o2 eliminator....Thanx...

 

geldyTSI are you getting creep with nitrous?

I don't get any creep with a 75shot. I can run 14psi minimum with no creep. I don't have a ported wastegate hole either. I don't think you should have a problem iwith the 14b. With race gas you can run up to 20psi on a 75 shot.

 

I am not spraying any....i get boost creep without even spraying NOS...for some reason my friend told me a big16G needs back pressure... when i installed my 3" exzhaust it creeps up to 9 psi more than my initial setting..its crazy thats why i bought a hALLMAN ES still the same thing...its very weird...would it be my actuator...? its driving me CRAZY....

 

I just installed my NOS wet kit and am having major boost creep. I am running a big 16G and a 50 shot so far. I'll set the boost at 10 PSI and nail 20 easily in 2nd gear. I cant figure it out and need some pointers too. I am arfraid to take the car past 5500. I am getting 10PSI creep before 5500 RPM. I even checked the filter on my boost line to make sure it wasn't getting filled with N20.


Here is what I have...

HKS F-CON
HKS EVC
HKS EGT and Boost Gauges
550's and 3 HKS pumps
block and head decked (about 10/1 comp.)
HKS Sport (old ones are big 16G's)
Bushur FMIC
NOS wet kit
2.5 mandrel turbo back with no cat and welded race muffler


Someone please help me before I grenade a very new and expensive motor (less than 2000 miles).

 

I ran a 55 shot on zex, with a fp big t-28. My initial boost was 18 and when i sprayed i hit 25 psi, way more than i wanted. I was running 110 octane but i still detonanted casuse i wasnt tuned for that high boost. Only reason i used the zex was to keep temps down on stock smic. 2 bent vavlves after wards cause denso plug broke off. I guess this doesnt helpanyone else but oh well

 

Yeah, I am running 118 Octane gas, but still shut it down before a large explosion happened. I can't even set the boost on my HKS EVC low enough to use the N20. If I crank the manual controller all the way down (10PSI normally), I am still hitting 20+ PSI before 5500.

 

IMHO 6-7cm2 housings are WAY to small for nitrous applications. Hell they are too small for big boost applications alone!

7cm2 is only slightly larger than a .50 a/r housing.

The problem is you have too much backpressure pre turbine. You get into a negative delta p situation where you have more pressure in the exhaust manifold than you do in the intake manifold and that's not good. You end up with reversion, higher combustion temps, higher cylinder pressure etc etc which all can lead to detonation and/or burned valves.

As an example we gained *80whp* by just going from a .63 A/R to a .82 A/R turbine housing on a T3/T4. Everything else was identical. Boost, dyno, conditions everything. Just a turbine housing swap.

6-7cm2 Mitsubishi turbine housings are too damn small for performance applications IMO.

 

My car must be a freak or something. I'm running an unported FP T28/28 with 6cm housing. I'm even still running the spacer ring on it. I'm also running an unported exhaust manifold. I can run a 75 shot as low as 14 psi and hold it to redline. But normally I run 20psi on the 75 shot. I also have a ported EvoIII O2 housing. Don't know if that might make a difference.

 

It also depends on how much air your motor is flowing. From what I understand the FP28 will support 111mph traps/hp level, so with the nitrous your using the turbo to it's potential.

I would still be careful about squeezing on a small turbine housing like that. Yea it may be "fine" but you probably have 35-45psi of manifold pressure. Sooner or later something will give.

I also have a hunch that your 2.5" downpipe is saving your butt a little in regards to boost creep. The pressure differential is not as great because you have some backpressure in the DP.

 

What can happen from too much manifold preasure? FP told me it has a 6cm housing. I guess most people ported to 7cm. I guess this is the with of the turbing side that connects to the exhaust manifold.

 

Look a couple posts above and you will see this:

The problem is you have too much backpressure pre turbine. You get into a negative delta p situation where you have more pressure in the exhaust manifold than you do in the intake manifold and that's not good. You end up with reversion, higher combustion temps, higher cylinder pressure etc etc which all can lead to detonation and/or burned valves.

And no that's not what the A/R of the housing is. It's the size of the "nozzle" area where the scroll inlet starts looking inside of the turbine housing. It's also can be thought of as overall "size" of the turbine housing.

Think of

.48 = Small
.63 = Medium
.82 = Large
1.04 = X-Large

Something like that.

 

Well the big28 and t28/28 are .48 ar. So mine is a 6cm housing with a .48 AR. I guess that's quite a bit of back preasure. Thanks by the way.

 

Hey no problem.

That was a real generalization. You have different "families" of turbo's as well. The T25/28 is what's called the "small frame" turbo so a .48 in that "family" is even worse than a T3 housing with a .48!

FP does do some custom port work on it as well so I'm willing to bet that they open it up a bit.

You can measure manifold pressure just by tapping into a runner and hooking up a pressure gauge. It's that simple. You can do the same for the entire exhaust system.

 

I just spent an hour pulling my EVC out of the dash and turning my "LOW" setting as low as it will go (9PSI). I went out and ran it and still....................25 fockin PSI at 5500.............yikes. I know my car has "mystery pistons", but it also has "mystery rods" and I have high compression. I dont know how many 25PSI blasts it will take before it shoots parts all over the highway and hopefully onto the hood of some Ghetto Sled that is big pimpin in the fast lane on 20's....

 

quick 25 psi bursts won't hurt it. I've done a few 30psi bursts before. They where very quick and I imidiately let go.

 

Yeah of course it wont do nothing....just pull your timing...my car without spraying goes up to 25psi...its crazy...im trying everything...and this happends with boost set at 10 go.damn psi....what would be more logic to u guys a 300 external wastegate or a stupid polished o2 housing with vented wastegate tunnel.....210$

 

Well, I am assuming that it over 20PSI, my HKS gauge goes to 20 and it's pegged. After a discussion with one of my Porsche buddies (944 Turbo 600+ WHP), he seems to think that my internal wastegate is the problem. He thinks that the spring might need to be swapped for a lighter spring. His concept is that it is hitting so hard, that it isn't bleeding off. He also seemed to think that the N20 is playing havoc with my F-CON and HKS EVC.


As far as timing goes, I have and Electromotive EV1 Ignition which is programable. I am going to assume (was installed by previous owner) that it is stand-alone and the ECU does not pull timing. I looked at the settings last night and here is where they are at.....


Base timing: 12 deg
Advance @ 3000: 24 deg total
Over-rev: Retards timing to -8 @ 7500


I tried turning the HKS EVC completely off last night and hitting the juice, same thing............slammed up to 20+ PSI. I made a quick blast and pulled the plugs. They looked light brown and a bit "gritty", I would assume from the leaded gas. I didn't see any discoloration. Does anyone have a pic of a plug with signs of detonation??

 

By "gritty" do you mean they have little specs on the porcelain and/or a rough texture like the "specs" are tiny little welding "tits".

If so, that's detonation chico.

 

getting closer....

Naw, it is on the metal of the plug, not the porcelin. It looks like tan primer was sprayed on it. After an in-depth discussion with our dyno guy about this situation, here is what his .02 was (and he has been settign up DFI systems and running a dyno for 15 years). He says that my boost gauge is indicating a false reading because of the N20. If my boost is set at 8psi, thats all it is putting out, the N20 is just causing a false reading for obvious reasons. What should I have my timing set up at? Any suggestions?