dustin

So, after a couple months of being down... I finally got my GSR back boosting again. Equipped with a brand new 3" Thermal exhaust and 3" Arturbo (modified by me) downpipe, I decided to terrorize my local town.

I have a .5 bar spring in my wastegate (might be .45, I forget). Pressure for the wastegate is tapped to the compressor. Everthing is installed properly.

I left the AVC-R settings that I had for my old exhaust [.5 kg/cm^2 (7.1 psi) boost, 45% duty cycle]. I was in second gear and got on the throttle maybe 75%. By 5k rpm I was seeing .55 kg/cm^2 (7.8 psi)

I made my way to an isolated road, and I wound out second gear to 7k rpm. I was really excited to feel that the car had SO much more top end power. Then I checked the AVC-R and peak hold showed .79 kg/cm^2 (11.2 psi). I had not even hit redline

So I set the AVC-R to 30% duty cycle across the board, and wound out second gear. By 8k rpm I was still seeing .65 kg/cm^2 (9.23 psi)

Then I set the AVC-R to 20% duty cycle (the lowest possible setting). I got .62 kg/cm^2 (8.8 psi)

So, as a last ditch effort, I set the AVC-R to off. The lowest I was able to hit was .59 kg/cm^2 (8.4 psi)

Now, I would like to boost exactly .5 kg/cm^2. None of this .79 nonsense. With the AVC-R off, boost is not fun. From 3500-5500 rpm I make almost an impressive 5psi, and by 7k rpm I am making 7psi, and after 7k rpm it spikes to 8.4 psi or so.

I suppose I could get like a really weak wastegate spring, and use the AVC-R to compensate... but that is just a band-aid solution. I think Kabir is right, the DRAG manifold just causes spiking with a freeflowing exhaust. I guess I could get a revhard manifold and get my downpipe entirely redone (Just finally got it to fit after ages of effort).

Any ideas?

Dustin

Rob03Pro5

Well before you go and get a new manifold and dp, check all your vacuum lines. Are they in good shape and are they large enough?

I would also tap the wastegate vacuum source to somewhere after the intercooler instead of the side of the compressor.

I'm not too familiar with your old setup, but did you have the AVC-R before? Doesn't the AVC-R have "fuzzy logic" and needs to relearn everything? I would check into that also.

Just for the hell of it, try installing a MBC (if ya got one, or can borrow one) and see if that solves the problem.. if not, maybe your spring went bad?

dustin

I just replaced all of the vacuum lines. All wastegate lines are 6mm. They are connected properly. The BOV, Vortech FPR, Boost gauge sender and AVC-R sender are tapped off the brake booster line.

Tapping the wastegate after the intercooler would theoretically give me more boost w/ the AVC-R off. I want less.

Yes, I had the AVC-R before. It relearns when you change the duty cycle. Each time I set it to a new duty cycle, it relearned the duty cycle curve to no avail.

Installing the MBC would not help, because boost even spikes when I have the AVC-R disabled... boost is only being regulated by the wastegate w/ the AVC-R off.

Since the spiking is linear with RPM, I am led to believe that it must be exhaust related.

Maybe I could try porting the entrance to the wastegate on the manifold... I guess it could not hurt.

Dustin

JM Performance

From what I've seen and heard it sounds like it has to be the manifold. Think about it, gas wants to go where there's the least pressure possible. Now that you have so little back pressure from the exhaust (normally good), gas wants to go there instead of to the wastegate.

Sorry, but it sounds like a new manifold might be the only solution.

dustin

Seems to me that I am too the point that even if I bleed all the exhaust off cyl1, cyls 2-4 can flow enough to overboost...

Dustin

LsTurbo91

Dustin, I tried that also, it helped a lil when I only had a 3" exhaust then when art's downpipe came its all over. You'll notice you can port a little on the top right because the gasket doesn't line up properly with the hole. Save the hassle and get a max rev manifold, it wasnt too bad re doing it again but guaranteed your problems will be solved! It seems like the wastegate is quieter as well with this manifold. and no one believed me either, looks like your case #3



[Modified by LsTurbo91, 7:15 PM 10/30/2001]

dustin

Well, drag manifolds suck then. DRAG

LsTurbo91

I know what you mean man, especially after waiting forever for Art's downpipe, (no offense Art ), and then this comes up .... can't blame the deltagate forever.... that's why my friend couldn't believe I was having boost creep problems with a External wastegate! and his little dinky internal wastegate is hanging at 16psi of boost with no creeps like I had .

You know I was looking at the rev hard's manifold does all 4 runners meet with the wastegate? It looked like it was only on runner #4?

dustin

So, which manifold did you get? Did you just modify art's dp? I better start saving my pennies. My CRX LS project may have to wait (the CRX will get the drag manifold though...so I guess that is a plus... hehe)

DIRep972

iTrader: (1)

Are there any Revhard owners with boost spike w/ the tial + 3" DP/exhaust system?

If they are not spiking most likely its the manifold issue...

The other day I remember art telling me his boost gauge is only reading 6.5psi instead of 7.35.. He has the .5bar spring.. go figure he is loosing boost, I dunno what from though, it would probably be better if he explained..

anyways I was wondering about this too because on all factory turbo cars when you put a free flowing downpipe and exhaust on the boost level is changed and i had never heard of people talking about this on honda/acuras..

LsTurbo91

I have a max rev manifold, I just modified art's dp, this is actually the 2nd time since the 2nd time I got from him it was too long. All you have to do is cut it right before it flares to a 3 inch one of the welds before the 3 inch, then cut it from the flange and rotate it just a bit, reweld it, add an inch or so, your done. This is the time where you need your "MIG welder" that you left on your other pants!

I'll take some pics tomorrow if you need some pics. The turbo is a bit higher and straight, doesn't angle like the drag manifold, I don't know if it will have a significant effect on your filter piping.

Synapse

I'll almost bet anything that it has absolutely nothing to do with your manifolds but more so with two things:

1) wastegate, not much you can do about it

2) Your wastegate dump is vented into the atmosphere isn't it, and not routed back into the d-pipe?

to #2 think of it this way, the pressure delta before and after the wastegate is relatively high and is more influenced by atmospheric pressure and temperature the shorter the dump exhaust is from the wastegate, especially if there is no dump and straight out the flange of the wastegate, the delta is even larger, making it even more unstable. If you don't have a dump tube get one, you won't lose power and increase stability.

To #1, setup the AVC-R in the advanced options, where there is pneumatic signal from the solenoid both above and below the diaphragm to maximize valve closure under vac and feedback stability under boost.

dustin

I have a dump tube that extends to the bottom of the car.

The AVC-R only works by regulating pressure to the top of the diaphram on an external wastegate setup.

Dustin

dustin

I am thinking of just buying a wirefeed welder and learning to weld. Cheaper and then I can do this nonsense myself.

Dustin

ken

Just curious, but have you seen the Drag manifold? On the Drag, the wastegate sits on the 1st runner, so the other 3 runners do not get equal access to it. At high rpms with a free flowing exhaust, it would be easier for the other 3 runners to go through the turbo than to fight their way to the wastegate.

Additionally, I would think opening to the atmosphere would be better... less back pressure. If it goes down the exhaust, it would then mix with the back pressure of the exhaust system and a little 35mm wastegate won't be able to flow quick enough to keep it from going through the larger turbo hole.

I am no expert, but just looking at it with some common sense...

LsTurbo91

You know I've also been debating that for some time now. I would have bought mine if the muffler shop i go to charges a lot but they don't so I can't complain.

Synape: How do you explain it then if its not the manifold, I would have had the same issue with the max rev manifold?

LsTurbo91

Your right, but there is no possible way the pressure can go up the runners they are all seperated until they meet at the turbo.

TurboInteg95

a wire feed (mig welder) wont work for making manifolds. Manifolds need to be tig welded, you need the extra penatration you get from TIG. the Mig welded manifold will be cracking every so often. Dustin, do you know a welder, you can probably modify your manifold so the wastegate is being fed from two of the runners. It will have to be TIG welded though.

Synapse

i guess it's not the dump tube then, but you may want to play around with the avc-r and how it's setup relative to the wastegate, there is a reason why there are ports on the underside of the diaphragm.

either way, I think that its the gate or have you tried disco'ng the avc-r solenoid altogether and see what the stability is like?

dustin

With the AVC-R off, no pressure is sent to the top of the diaphram.

Dustin

Synapse

i guess that the effective pressure exactly at the exhaust port vs mid-runner vs collector are all different, but from experience, having taken pressure readings across runners, there will be an effective mean pressure across the entire manifold that equalizes.

Yes the engine pulses and it is entirely conceivable that the WG is getting more attention from one runner vs another, however, the wastegate acts as a feed-back controlled valve that will self-adjust based on the boost pressure that it is supposed to maintain (ie (pi*r^2):volume ratio).

So I tend to think that the WG is a big contributor.

Just my thoughts, but the manifold will have a mean pressure in any runner, even at turbine entry, but the WG self-regulates on pressure signal from the intake maniold . . . if you are taking boost signal from the compressor, you might wanna try signal from right before the throttle, for boost pressure that is more responsive to what the engine, ie intake, actually sees. There might be a time delay factor in the feed back loop from the time the boost pressure @ time 0 (compressor) vs. what the wastegate is actually regulating in the intake, I could be wrong

Synapse

are you sure, if that's the case then you're runnin of just the spring and the gate is opening up and leaking early in vac 2 boost trans, when the AVC-r is off, try it with the solenoid out of the loop and see if it is stable

Synapse

i probably spoke too soon but probably the main diff between the DRAG and the max rev is that the drag is designed for pulse exhaust turbine driving, whereas the max rev is more of a constant pressure manifold.

So the DRAG is more proned to possible uneaven pulse discharging out the WG.

However, consider that Pulsing requires less exaust manifold back pressure to spin the turbine, which is better for exhaust scavenging of the cylinder.

anyways, I'm probably rambling on.

dustin

I think I might just spring for the Hondata and put my 550cc injectors in... and use the creep to my advantage. I'll just drop my crowers and JEs in.

Dustin

chri5

way to go. Dont fight the boost, embrace it.

Damn i guess since I have the exact same thing as you when i get that DP on there I'll have to worry about the boost creep too. Oh well.