Tell me why I shouldn't run 10 psi of boost...

[qsiguy]

Power corrupts! I'm at 8 psi and I want more! Methanol took care of my detonation, AFR's are good and adjustable, injector duty cycle is ~80-85%, MAF is a little over 4 volts....

Tell me why I shouldn't shoot for 10 psi (or until I max injectors or MAF), if I have a little room on the injectors, AFR's are good and no detonation, where should I be concerned with the mechanicals? Any known limits on the stock motor? I know darinz is running 10 psi, just without VCT and a lower rev limiter, I assume all stock internals.

Somebody stop me!

[AZhitman]

Tell me why I shouldn't run 10 psi of boost...

Because you should run 14.

BTW, why haven't we met up yet? I need to see this beast!

[qsiguy]

No doubt I love showing off the turbo! I met you at the last NOPI event, not sure if you remember.

14 psi huh, I don't know about that! LOL

[konatown]

What does slim run in his 450zxtt?

Anyone contact Nizpro and see if they tested the stock internals of the VH45DETT before they made their race boat?

[elwesso]

Slim runs 9psi springs in his actuators..

10 PSI with meth (heh) shoudlnt be unattainable. Its just hard to gauge how close to the ragged edge you are!

[qsiguy]

Ya, that's my concern...and the fact that I have almost 170K on the clock!

[qsiguy]

I did a little testing/logging tonight and I think I'm done at 8 psi. Might be able to squeeze 9 but I don't think I want to be that close to the limits. I'll post a screenshot below of the log. It was a bit rich at some points but mostly low 11's. I'm posting a video of that too.

Max #'s logged @ WOT:@ 50mph / 6400rpm / 4.88v MAF / 88% duty cycle@ 97mph / 6725rpm / 4.94v MAF / 92% duty cycle

[tmorgan4]

At what point do you need to start worrying about the intake and injector gaskets? I've been wondering how well those rubber rings (mainly the ones that seal the injectors) hold up to 8-9-10+ PSI.

[Chrispy300]

So what's the go with these engines when you run out of MAF capacity? Run two and half the signal AKA Z32 ghetto style? The skyline guys over here just grab a Z32 one and wack it in. Any easy solution for us?

[Carl H]

mount the z32 sensor in the q45 housing and retune the ecu...

[elwesso]

Something I might also make sure is you never lose any fuel pressure... Do you think is that a concern? It may not be a bad idea to hook a pressure gauge up to it, but increasing the FP a little bit might allow you to get to 10lbs.

[Carl H]

tru that, nothing like a bit of base pressure increase for a few more cc's of fuel.

[qsiguy]

Yes, I do need to check my fuel pressure. It does look like my numbers are pretty consistent with others I've seen. I suppose I could lean it out a bit and lower the duty cycle but it looks like the MAF will be maxed out as well.

Is it the MAF that maxes out at ~5v or is it the ECU that won't read any higher than that? If it's just the ECU that won't read higher than that, it would be pretty easy to offset the MAF voltage and then retune the fuel map to match. I don't think this would work if the MAF won't put out any more than ~5v. For example, if the MAF voltage was at 4v you could offset and send a 3 volt signal to the ECU. Anyone know where the bottle neck is?

Isn't that what AFC (air fuel controllers) do? Offset the MAF voltage? I've heard there are RPM specific ones that prevent over rich conditions at low rpm. Wouldn't be necessary if you can tune the fuel map tho.

[elwesso]

I believe the reference voltage for the MAF is 5 volts, so it cant read higher than that, if memory serves?

[qsiguy]

That's what I had previously thought but a few months ago I was doing some research on MAF's and the FSM shows this one getting battery voltage. The other two leads do go to the ECU. Is this a frequency type MAF? I check the three wires with my voltmeter at idle and then revved it and none of the terminals where indicating at 0-5v output consistent with the reading the ECU provides. The FSM isn't very specific on what these wires should read. It is more concerned with whether or not they have continuity with the ECU terminals.

If it was just a reference voltage, that would be easy to change but it doesn't look like it will be that easy.

[Stinky]

I'm pretty sure the limit is due to the a/d converter in the ecu. I believe the limit is actually 5.12v but I could be wrong. The maf is definitely voltage based like all of the other nissan mafs.

[craigztoyz]

Just curious, I havent had to customize Maf's, just bought aftermarket from like C&L n such.

Could you increase your chamber size, and adjust the Maf readings accordingly?go from 90? to 95? put stock sensor back in and let it read the same #, but actually be getting more air?Wasnt sure how much you can build your tune, and how feasable this idea was. Similar to running 2 Mafs and only using 1 signal, or splicing it.Just curious, and gotta say, love what you are doing! More videos please

[hannibal]

I believe the MAF reads xxx amount of air and outputs a corresponding voltage to the ECU. Its maximum output is ~5V.

[qsiguy]

I've heard of people installing the sensor in a larger tube before. I believe it can work. As long as you know how to alter the tune to match it shouldn't be much trouble. I'll have to give this some thought. It may not make any difference anyway unless I get larger injectors. Either way I'm going to max out something very shortly.

Thanks for the compliment. It's been a long time coming but now I'm getting the reward. It is a blast. I love videos too. I'll get more online shortly. If all goes well with my schedule I may be getting a dyno done on Saturday....There will be videos!

400 whp?

Any guesses?

[elwesso]

i bet you're pretty anxious to get in some 555cc injectors and a valve body for the trans....

Great project shane, as Ive said before this came out LIGHTYEARS better than I thought it would. Props for taking the unique route and having it pay off!!

[craigztoyz]

I've heard of people installing the sensor in a larger tube before. I believe it can work. As long as you know how to alter the tune to match it shouldn't be much trouble. I'll have to give this some thought. It may not make any difference anyway unless I get larger injectors. Either way I'm going to max out something very shortly.

Thanks for the compliment. It's been a long time coming but now I'm getting the reward. It is a blast. I love videos too. I'll get more online shortly. If all goes well with my schedule I may be getting a dyno done on Saturday....There will be videos!

400 whp?

Any guesses?

408 torque, 390's hp. hope it breaks 400, on hp, but torque matters more, n from the videos, id guess that you are close.

[hannibal]

I've heard of people installing the sensor in a larger tube before. I believe it can work. As long as you know how to alter the tune to match it shouldn't be much trouble. I'll have to give this some thought. It may not make any difference anyway unless I get larger injectors. Either way I'm going to max out something very shortly.

KA turbo guys used to called that a hacked MAF. Supposedly, if you increase the diameter of the tube by xx%, you can increase the injectors by the same xx% without needing to retune. This was run on several KA-T's. A guy called orion comes to mind. He has a dyno showing his hacked MAF (using 370cc injectors) making more power than a JWT tune.

[Stinky]

Only problem with doing it that way is that it also affects your timing. If you can compensate then you're fine but it's something to keep in mind.

[tmorgan4]

I just read something on the Nistune website that could solve the MAF issue....It mentions installing the filament in a larger tube and re-calibrating. Seems like a good idea.

[qsiguy]

Did you read above? We've been talking about that for a couple days, lol. I know at least one person that did it successfully.

Here's a clip I found on the Nistune site. Is this what you found?

"To get around the MAF limits, people are now doing the following:

(a) using the MAF in a larger tube and recalibrating to suit(b) using MAFs from Toyotas and Fords with the Nissan ECU or(c) using two MAFs with an Apexi SAFC to combine the signals"

[tmorgan4]

My bad....I did read the above but didn't realize everyone was talking about doing the same thing.

Also, did you see the part that mentioned the two emulators Nistune recommends? There was another site besides Moates.

[T45]

Not completely off topic but the thought of taking my MAF sensor and just putting it into the 3.5" tubing in my intake sounds trick. Any ideas how much difference it would make airflow wise adding 1.1 mm to the i.d. size?

[elwesso]

its not the DIAMETER you want to concern yourself, its the cross sectional area!!!

So if its a 90mm diameter MAF, thats 6361.73mm^2

If you want to increase that by say 1.5, that would give you 9542.59mm^2, then backsolving the area equation (rt(4/piA)), you get roughly 110.23 mm, which is ~ 4.3in.

if you just multiply the diameter times 1.5 you get 135mm, which is of course not the same thing.

Just food for thought... You'd probably want to run 4.5in tube, which is 114mm, which would increase your area by about 1.6 which would work really good.

another thing id concern myself with is as you increase cross sectional area you put the MAF element farther away from the center of the area, which of course as we all know the turbulence increases the closer you get to the wall of the pipe.. I would be concerned about going up to an increase around or above 2.0 because the MAF may or may not get an accurate reading...

[Jeff Taylor]

Boost pressure doesn't matter as much. The amount of power/torque you're making and how well it's tuned is what matters.

6psi on my 72mm turbo or 22psi on a t3/t4 will both make the same amount of power on my engine.

You cannot judge whether an engine will hold together by only paying attention to boost pressure. There are many other variables to keep in mind.

I'd say you'll be fine up to 450 wHP on 93 octane, no matter what boost, so long as it is tuned correctly. Who knows, maybe 600 wHP is achievable on 93 octane.... You'll just have to find the threshold of detonation.


Modified by Jeff Taylor at 2:01 PM 4/24/2008

[T45]

Hey Jeff, long time no see. Why you holding out on us MAyN?

http://vids.myspace.com/index....74071