I had really low timing before. Low timing + rich a/f ratio means more potential energy left in the fuel which was transfered to the turbo, meaning faster spool and more boost. Once we added timing to where it should be, the boost dropped about two full pounds. This is only because I had 0 boost control at the time, the WGDC tables were all zeroed out. So I've run it that way, with all of the control system turned off in the ecu, just not with the line run right from the compressor to the wastegate. It's an external wastegate.

That's what tial rates them in is "bars", so I have a bad habit of doing the same thing even though it's not technically accurate like you said I'm thinking once I get everything sorted I'll run 21psi of spring pressure.


I have run up to 32psi just by adjust wgdc, and my boost curve is fine right now, it's just the noise that's driving me nuts Also I want to make sure I'm not mechanically hurting anything. At first I was worried it was compressor surge, but if it's wastegate flutter than it's more or less me just wanting to get rid of the noise.

 

I'm sorry, i don't mean to keep going off subject or trying to call you out but i just don't want bad info in people's heads. So if i may, this is incorrect. Since we know that energy cannot be created nor destroyed we know that the turbo is a mechanical device utilized mainly to transfer thermal energy into kinetic energy. meaning it uses the unused gases to spin the turbine wheel etc etc. It CANNOT extract the "unused potential energy from the fuel" like you described. However, there is a case where if enough overlap between the exhaust and intake valves happens in combination with SUPER low timing (literally not enough to ignite the fuel) and TONS of fuel are added, the phenomenon of Anti-Lag happens. In which, the turbo acts like an engine literally igniting the fuel in the turbocharger which then spins the blades and makes it spool. but this is highly detremental to turbo, but it sounds bad *** and aids with spool loss during shifts and is why rally teams use it amongst other reasons. anyways, i don't think you were anti-laging either. so i don't know how you lost 2 psi from timing. never heard of such a thing. just my .02 cents.

ps. are you sure it's not your bov that's leaking and making that fluttering noise? i haven't heard the clips so.

 

I probably didn't describe it right, wrong terminology or something, but I didn't say anything about creating or destroying energy. When I first started talking to ETS about the possibility of compressor surge, they brought up the fact that some people over-spool the turbo at low RPM when they have too low of timing and run rich. Fuel is potential chemical energy. If you have extra fuel, and low timing, your not starting the combustion process early enough for it to completely turn all the potential chemical energy into mechanical/kenetic energy in the combustion chamber, so some of the process (in theory) can finish in the exhaust. This can in turn spool a turbo faster. Rotary engines do this just as part of their normal operation, one of the reasons they have such horrible emmissions, but also one of the reasons they can spool relatively big turbos with such small displacement.

At any rate this is not ideal, and doesn't make the most power possible. When we fixed my crappy timing, I did lose spool and 2 psi, I can show you the logs, but since the potential chemical energy from the fuel is now all being extracted in the combustion chamber like it's supposed to be, I picked up 50hp and 45 ft-lbs of torque, even with the loss of boost.



Yah, checked the BOV first. It's a synaptics BOV, haven't heard of any of them leaking, but I did check. I do need to do a full leak check again, I've messed around with it a bit since the last one and I could have popped something off. Ah the joy of cars

 

The only way the turbo could extract power from the unburned fuel passing by the exhaust is by igniting it in the turbo. Anti lag. So you were anti laging? Or are you saying the turbo extracts potential energy from the fuel passing by it magically? How else in the world could a turbo spool faster from low timing and rich afrs otherwise? I don't know or claim to know everything but do tell.

Edit: what you're describing would be ignition so perfectly retarded that it would almost have to be in the exhaust stroke of the cycle for it to "finish in the exhaust" and that would be very bad power wise since the flame front would be horrible and work its self against the piston.

 

Exactly, it's very bad power wise, but it did help the turbo, since the ignition cycle is started so late, it has a poor flame front that doesn't finish burning until it's in the exhaust, so the energy is being expelled against the piston on it's up stroke (but since the valve is open, it's not pushing fully on the piston), and as it's passing the turbine.

It's not magic, because your absolutely right, there is no way for a turbo to extract potential energy from unburnt fuel, it would have to ignite it. But if the fuel is burning (even if it's the very very tail end) it can transfer that energy to the turbo. Just like people wrap/coat a turbo, manifold, etc. to keep thermal energy in, the heat and energy are transfered to the turbine from the burning fuel.

Again, it's NOT A GOOD WAY TO DO IT. I'm sorry I didn't explain what I meant well, I wasn't trying to say unburnt fuel makes a magic turbo, I promise I'm not that crazy With the tune the way it was, the low timing was working against the engine. I was getting ignition break-up up high, the flame propagation was horrible, but spool was great! Like I said, I lost boost with the tuning, but picked up HP and Torque. Normally, you would probably never even notice that effect, but since I had no boost control enabled at the time (the BCS was hooked up but "disabled" in the ecu) it was noticeable.

Though again you're probably right, I shouldn't be building that much boost over the spring pressure unless I have a boost leak, or serious boost creep. But I wonder if just having the BCS in the vacuum line and not hooked up acted like having a pill in the line...

 

The only way to exact power out of the turbo like your describing is turn it into turbine....like a jet turbine and using its exhaust thrust.

http://www.pulse-jets.com/

Needless to say its hard to analysis whats going on with his set-up, because there is more going on there than what is being described. To clarify by the boost leak being talked about is REALLY a vacuum leak on the wastegate vacuum line. I think that is what criptballer means.

But again, if slight tuning is shifting the boost curve by 2 psi like he is talking about, then he has some other issues to be looking at.

Maybe let me read back through the posts and take a stab at it.

J. R.

 

OK I'm ready to take a stab at it.

If your hearing fluttering then the gate is opening and closing rapidly. So in reality we can say NO BOOST CONTROL is occurring because the gate is doing whatever it wants.

So is it mechanical or electrical?

Mechanical reasons:

1. There is a leak in the reference vacuum line to the wastegate. I used to do this on purpose on a older 2.6L turbo mitsu I had and the wastegate would flutter as you say. What can I say....cheap mans way of turning up the boost.

2. The spring is SO WEAK that the exhaust manifold pressure is fluctuating it. This usually comes from people trying to run high boost on a small turbine wheel. The wheel can't flow it so exhaust pressure spikes in the exhaust manifold and the air eventually finds its easier path to push open the wastegate spring then try and get through that small exhaust wheel.

3. The tune on the car sucks so bad that like criptballer was talking about, anti-lag, the timing being off to the point that explosions are occurring in the exhaust manifold spiking exhaust manifold pressures causing what I just described above in number 2. If this was the case I bet your manifold GLOWS pretty. :-)

Electronic reasons:

Well, I'll assume your using the factory ECU and solenoid so as long as you are controlling it correctly all should be fine. With other after market controller, especially the ones that the greddy and profect B use, the gain can be so high that the solenoids swing open and closed to much and you get the flutter and spiking, but you can control that on those controllers with the gain.

I highly doubt its a electrical thing since your just using the factory ECU with ECU flash to control it. And I'm sure your boost control table looks very linear and is copied to the multiple tables.

Anyway. Good luck

J. R.

PS I'm not very familiar, but aren't there multiple boost control tables? Like some for bad gas. What if you had not played with all the tables and its jumping back and forth between wastegate tuning tables on you?

 

Just one table for boost control, so that's not it on that one. Very linear boost control table too, you're right.

When you talk about mechanical, that's kind of what I'm leaning towards, but more in a different direction. What if, since the spring pressure is so low, when I'm running 26 lbs and the BCS tries to open the wastegate a little to start bleeding of excess pressure, the wastegate doesn't open just a little, it just slams open? The BCS would then try and close it again to bring the boost back in line, which would make the boost climb again, so it would try and open it again, and so on and so on? Does that sound feasible? I know a lot of guys say you shouldn't run more than double the spring pressure in boost, and I'm over that by a ways when I'm doing 26lbs.

 

Dear Sir/sensei,

are there any situations in which in a turboed engine's vacuum line doesn't boost while the vehicle is in boost? no at least to my knowledge. so since the problem is happening while he is IN boost and not idling or it would be a boost leak right? now if he was idling bad due to a a leak in his FPR hose or something, then it would be a vacuum leak

now JR, do you have any info on this " i lost boost because i adjusted my timing" comment? Do they correlate in any way as far as the timing controlling the boost directly or indirectly? could what he was describing really happen without this really loud noises coming out of his turbo happening from it igniting the fuel?

I don't think that's how a bcs works. correct me if i'm wrong JR, or anyone else. a bcs is either interupt or a bleed off type. meaning, if you have a spring rate pressure in your actuator of 10 psi and you want to run 21 psi the bcs is either going to bleed off 11 psi or it will interupt 11 psi (meaning, it will interrupt 11psi with high frequency pulse width modulation) so that the wastegate doesn't "see" this pressure, but it's still there. but the bcs doesn't progressively open and close the wastegate like you describe. when the bcs reaches the desired psi through duty cycles (or how i like to think of it, how hard it works to stay closed) then the rest of the air is "seen" by the actuator which then opens up, on and off switch.

edit: your interesting theory of spooling a turbo faster with rich afrs and low timing made start a thread about the subject alone FOUND HERE

 

See I still think the fuel is already burning from the ignition cycle inside the cylinder as it enters the manifold. Or it just is making the exhaust hotter from not having a complete burn as it should, finishing the burn on the pistons up-stroke. Like you say, if the turbo was igniting the fuel you'd hear it. But just so you know, I'm not talking about having added a little timing, I had to add A LOT. like 7 degrees+ in places. Maybe what we should do is if the roads get clearer, we should get together and I can load both roms back to back, run down the same stretch of road, and see if we can figure out what else it could be, cuz I still think it has to do with the heavily-retarded timing and rich fuel. Just like Mitsu has lean-spool conditions to help with torque during turbo spool up, this is killing torque to help the turbo spool... errrr something



Yeah, the stock BCS is a bleed type, meaning it bleeds off excess pressure to keep the wastegate closed longer, but this is worse for boost control because you're limited to what the BCS can bleed.

The Grimmspeed is an interrupt like you say, but that means it's either open or closed, so say at 26 psi when I have the duty cycle dropping from 100 (always "closed") the BCS starts to modulate, and the wastegate is either seeing 0 or 26 psi. So if it just has an 11 psi spring, when it goes from seeing 0 to 26psi and back and forth, that thing is probably flapping pretty good since there's not much strength when it goes from 0 to 26psi and back again so fast. So that's why I'm thinking going to something like 21lbs of spring pressure would help alleviate the problem. Does that make sense at all?

 

My understanding of lean spool is to AID spool. not to diminish it. why would mitsu want laggier set ups? and this helps my thought, leaner conditions creating MBT pre spool to help flow as much air throught the motor and helping the turbo spool faster.

I'll get to your last comment later cuz i'm at work.

 

arent you on a external gate? I have always used a MBC and had great results. my car held rock solid boost, no spikes or dropping or surging and thats even with a internal gate

 

See my understanding is that lean spool was to aid torque while the turbo is spooling. The stock turbo is small enough that it doesn't really need extra help in spooling, thus lean spool = leaner conditions, higher advance to aid in low-end torque during low boost times.

Yup I'm on an external gate. One of the reasons I'm using ECU boost is the per-gear, per-rpm ability to control boost. I'm not much of a drag racer anymore, so this car is being built more towards road-racing. Hence the ball-bearing turbo, the water-cooled wastegate, etc. Being able to run custom boost profiles will help when I go from auto-x to miller etc.

 

i think the 11lbs spring is hurting you, i always try to start with a spring pressure of what the lowest boost you plan to run, like if 20 is average get a 20lb spring

 

Yah I think that might be it. I think I'll run to Rally Sport today and pick up some springs for the WG.