Sapphonica

I have a GReddy kit & boost controller and am working with a tuner to get the most out of my 8 without popping the engine again.

It's been ported, and is using a skunk works standalone ECU that will allow us to control the secondary & tertiary ports.

Theoretically, we should be able to get more power at mid rpms by increasing the mass flow rate via tweaking when the ports open.

Has anyone actually tried this yet and/or have any substantive information to share before I charge in as the 'crash test dummy'?

Thanks.

IZoomZoomI

ahh skunk works...

Sapphonica

'skunk works' as in 'cannot disclose the vendor' as opposed to a specific brand!

MadDog

I was actually thinking of disabling the APV motor. I notice that the boost falls-off at the same time as the third runners are opened. This also coincides with a lean spike at precisely the same instant. I haven't really thought it through yet, but I am guessing that 1) the additional volume present when the third runners open is just too much for the little turbo to keep up with, and 2) that the sudden influx of air is what is causing the lean spike. There are no fuel injectors in the third set of runners.

Like I said, this is half-baked, but I do know that the lean spike, boost droop and VDI opening all occur at about 6000RPM quite consistently. I believe it is due to the opening of these runners. I want to try keeping them CLOSED.

Moostafa29

I got mine tuned at Full Function Tech in Union City. They have a lot of experience with various ecu. You may want to give them a call. As far as port timing, the only person that I think has messed around with that is Dean (Xyntax). You may want to give him a pm, and see if he could lend some advice.

Beodude123

You know, I just asked about this not too long ago. Something to control when the ducts open up. Every (NA) dyno you see has a drop at each point of the variable system kicking in.

zoom44

Why would it be lean? the stock pcm over fuels when they open to keep it from being a too lean point. That’s partially why the hp line drops on the dyno. You definitely don’t want to keep it closed- you want to keep it always open for a turbo

MadDog

I suppose that it would be lean because you have a lot of air suddenly coming in with no fuel mixed in it. I definitely didn't see a surge in the duty cycles of the injectors when I was logging them over the last few weeks. There are no injectors in the tertiary runners. Maybe it takes an instant to reach a mixing equillibrium. You know, there could also be a dip in power due to a lean spike, not just a rich one. I'm not sure that you could see this spike with the smoothing the dyno shops do. Its pretty fast.

That being said, I think that lean spike is much less pronounced now that I am controlling the P2's like I am. I wish I could post a graph, but I'm traveling right now. It's uncanny - right at 6kRPM (or there abouts), there is a lean spike and the boost starts to fall-off at the exact same instant.

If you can fill the combustion chamber using only 2 of the ports, why would you necessarily want to have all three always open? It seems like just more volume that you are asking the turbo to pressurize without needing to.

rkostolni

The quantity (mass) of air that enters the engine is important for making hp, not the pressure the air is at. People port engines because it increases the flow capacity of the engine. By opening up the tertiary ports you have increased the flow capacity. If the boost falling off is due to the ports opening, then its just because the Greddy turbo can't flow enough to sustain the pressure you're aiming for. But you are better off with the increased flow and less boost pressure as a result of having them open. It means the turbo isn't working as hard and you'll have lower intake temps and even though the boost decreased, the flow itself has remained constant, or possibly even increased slightly due to less restriction.

I don't think it would be good to have them open all the time either, as that would hurt off boost response. Instead having them open at a preset pressure >0psi would be ideal.

r0tor

iTrader: (1)

i'll give you a warning - if the ecu goes to open the secondary ports and finds them already open, it will throw a CEL because it thinks they are stuck open

MadDog

I agree with you. Its the mass that's important. That's why I qualified my statement with "if you can fill the combustion chambers". Porting just helps you get the air and exhaust in and out more quickly - which pressure also does (and maybe does better?). But, if the combustion chamber can be filled to capacity in the time alotted, then fill pressure seems to be the variable that determines how much air you can stuff in. It just not going to take in more unless the pressure is higher. (again, if you don't have to worry about the time available to do it) Given that you can get the air in the chamber during the time available using only the first two sets of runners, asking the turbo to also fill the othr intake runners doesn't make sense. Just my thoughts....


BTW: Am I the only one who has logged the lean spike and the boost droop occuring at exactly the same instant?

rkostolni

But the pressure dropped when the ports opened because the flow was increased. Pressure and flow are inversely related. A flow increase means less restriction. So the turbo isn't working as hard and won't heat the intake charge as much. Imagine trying to feed the engine through a straw. Yes the pressure would be huge, but that isn't going to give you alot of power because there isn't enough flow. By opening up those intake ports you increase the size of the straw the engine can breath through -> more flow, but less pressure.

zoom44

oh right- forgot for a moment. there is a cel for stuck open but not stuck shut

MadDog

rk...
I don't feel like you read my post. I agree with you. What I am saying is that just because you have more passages to get air into the engine doesn't mean that the GReddy turbo can take advantage of them. You say the flow rate increased. You could speculate that its flowing faster through the turbo, but you can't say that there is any more mass flow into the the engine! Afterall there are several more feet of empty space to flow into all of a sudden. The problem is that the GReddy turbo CAN'T flow any more. If it could, it would! It would maintain the pressure when those runners open up if it were able to, right? I mean the wastegate is closed and its not ABLE to get to full boost. Its not suddenly going to a more efficient state of operation. Its incapable of maintaining boost because it can't flow any more air. If it could, it would. What else would stop it from going into full boost?

Besides, has anyone with a boosted 8 ever felt a surge in power when the intakes open? I certainly haven't. I don't think its going to buy you anything to open them or keep them open for this turbo.

Sapphonica

The boost controller is limiting the boost to x psi...that's what's stopping it from going to 'full boost'.

Funny you should mention a power surge when intakes open. Just today, I finally revved the engine past 7k, and WHOA! did I ever feel a surge when the tertiary intake ports opened! This didn't happen with my old setup, but now that I'm ported and have bigger injectors, maybe that's the explanation...the engine can get rid of the extra air due to better exhaust flow.

Oh well, I'll know more on Friday when I take it for my first round of dyno tuning.

rkostolni

I am agreeing that the Greddy turbo probably isn't flowing much if any more air as a result of those ports opening. What am I saying though is that the less restriction in the intake path reduces the work the turbo has to do. So it may be flowing the same cfm, but it is not spinning as fast to do it. This means a cooler intake charge because the turbo would be operating more efficiently. With the Greddy turbo, I don't think it will make a huge difference either way. With a larger turbo it could be significant. But hey, try it out and see what happens. This was just my opinion.

MadDog

Ummm. no. We're talking about the boost drooping below the set point once you go past 6kRPM. My boost controller is at about 8psi right now. But it starts to fall at 6k and reaches about 5.5 or so at redline.

RK, your're right. We are all just speculating. Its easy enough to disconnect that motor. I'm going to try it tonight and report back.


MD

Sapphonica

Does your boost controller have an RPM offset? If so, that will fix the problem of the boost falling off at higher RPMs. The stock GReddy turbo will sustain at least 8psi up to redline...I myself have seen that as well as many others who post on this board.

MadDog

Okay. I just returned from testing out my theory. I was right. Its the opening of the tertiary runners that causes the boost to fall off and gives that lean spike. I just disconnected the APV motor. It takes all of 2 seconds. I haven't bothered to type in all the data logs, but the difference is quite remarkable. With the teriary runners remaining closed, the boost is very flat, even in 1st and 2nd gears. There is not even a hint of that lean spike any more. In fact, the boost even PICKS UP towards red line! It does the opposite of falling off with RPM!!

I did all this testing with the RPM offset feature turned off - not that that feature ever made a damn bit of good for me anyway.

So, the only thing that remains to be seen is whether the mass flow rate INTO THE ENGINE (NOT INTO THE RUNNERS) is greater for the lower pressure when the runners open, or the higher pressure with them closed. Its obvious that the turbo reaches its limit on flow when the runners open, hence the boost droop. Now we just need to see if the flow is wasted by filling the volume of the runners or not.

I couldn't be sure that I felt any difference in performance either way. Its probably a 10HP type thing which doesn't feel like much on 250!! I think dyno testing is going to be the only way to know for sure which way is better. I was actually thinking of going to the dyno tomorrow. If I do, I'll test how this affects power output.

This is for sure, though. Keeping the teriary runners closed makes the boost nice and flat, even in the tough lower gears. Boost actually picks up with RPM as you approach 8kRPM. The lean spike that always accompanied the boost falling at 6kRPM is totally gone.

I am leaving mine closed for now - even just because the lean spike caused by the influx of air is gone.

swoope

iTrader: (5)

good read. great job!

beers

adrian-1

Very interesting. Boost dropping off has been a big issue.

I've messed around with the E-01 rpm offset and I couldn't get it to go higher. Does anyone have some settings that worked for them?

I would love to be able to hold 9-10psi in the high RPM's. Now, can the stock injectors handle it, is another question.

rkostolni

Great results. I hope you decide to go to the dyno I'm very interested in how this effects things. I suspect as I said before that power will actually be down since there's going to be a roughly equal amount of flow, but hotter air due to more restriction. But, hopefully I'm wrong. Even if power is slightly down, this may be a good thing if we can eliminate that lean spike. If you do go to the dyno, it would also be great to see what happens with the ports forced open.

RENESIS_NEENJA

MadDog: so your holding boost to redline? if so is the power in the upper RPM's comparable to before? I was under the impression that the runners opening in the higher RPM's is what really gave us the kick in the pants? therefore if we keep the runners closed won't that hinder the high RPM power!?!?

MadDog

Acutally, boost is increasing as I approach red line. As I said, I can't really feel a difference either way. Let me ask you a question: are you boosted? If so, do really still feel a 'kick in the pants; around 6kRPM? I don't. Its hard to feel a kick in the pants with the turbo giving you a knee to the groin!

MazdaManiac

iTrader: (3)

Well, my experience is thus:

On the KL engine cars from Mazda (MX-6, MX-3, 626, 929, Ford Probe, etc.), the VRIS (Variable Resonance Intake System) was the cause of a lot of heartache for people when they added forced induction. Everybody wanted to keep it because it improved off-boost torque and such. Ultimately, those that just wired it open saw the best power and drivability.

When you are under boost, torque adders like that simply don't do anything but upset the flow. Now, I'd think the best situation is to have them OPEN under boost. Maybe the solenoids and motors could be hooked up to the boost sensor somehow. I'd say wire them to the VTEC output along with the temp dongle, but this would close them again after 5100 RPM.

The dyno is the only way to know for sure, though I'd want to see the intake temps as well to be certain the the turbo isn't working harder at high RPMs with the more restrictive, closed intake system.