RX-Heven

iTrader: (1)

With the E6X you all know that you can adjust the bar heights @ x rpm vs. load.
Is it possible to use this as a boost limiter? Suppose I do not want to boost any higher than 17psi, can I just excessivelly raise the fuel bar height at this load to flood the engine with gas? Are there any drawbacks to this?

YearsOfDecay

Yeah... fouled out plugs, crappy gas mileage, explosions in your mufflers (huge backfire) from all the unburnt fuel, stuttering from getting choked with fuel, etc.

RX-Heven

iTrader: (1)

Well I expected most of that. None of that is as bad as a blown engine imho.
Mileage would not be affected because the fuel curve would be normal (optimal) until 17-18 psi or whatever I do not want the engine to see. At this point, the ecu would be programmed to dump way too much fuel to cut out the engine.
We only get 91 here in CA so I don't want to pop another engine.
I only run the engine @ 14 to 16 lbs. so I shouldn't normally hit 17 psi or higher, but there can always be the unexpected spike when you least expect it due to a number of worst case scenarios.

So my question remains the same, would this work safely as a last ditch effort to save the engine?

Carl Byck

What about a pop-off valve? Not sure why more people do not use them, too slow to respond?

RX-Heven

iTrader: (1)

That is what I have 'heard' about them. They also seem like a pain to adjust to the desired setting accurately. Seems you could pop your engine just trying to adjust the spring rate to a high enough setting. Not to mention they are $100 give or take when adjusting the fuel curve is free.

RETed

They react inconsistently.
I don't have direct experience with the GReddy unit, but I have messed around with the HKS one.
We tried to adjust it for 10psi, but if you boost slowly, it would actually crack open at 3psi!
If you boost hard, it would open at 7psi.
I told the guy to get rid of it.

These thing should only be used as a last resort safety device.
They should not be adjusted anywhere close to max boost levels.
For example, if you're running 17psi, trying to adjust it to 20psi is pretty hard.


-Ted

RETed

There is a way to adjust the bars to use the fuel map as a boost limiter.
Ramp the fuel up progressively, and you don't get no huge fireball coming out the exhaust.
If you're going to constantly bang off the higher bars, then that's asking for trouble.
I typically do this for all my customers, as it's probably the safest way to prevent overboosting.
The driver should immediately sense the drop in power and lift off the throttle.


-Ted

RX-Heven

iTrader: (1)

Thanks Ted. Thats exactly the answer I was looking and hoping for.

Carl Byck

I'll bet the Pop off valve used on the indy cars was precise, I wonder what technology(design) they used? What is causing your spikes? What boost controller are you using? What wastegate are you using? Also, you stated that you had solved your boost control issue, what was the problem, and how did you fix it? BTW, I TOTALLY disagree with reading boost(for the boost controller, and FPR) off the compressor ALA Steves suggestion. You then have no idea of what your actual boost at the motor is. Not only that but you cannot hold boost as long(controller sees higher than actual boost, and sees it sooner), or build to your max desired boost at all. What about some sort of boost level activated fuel cut ala the fuel cut in stock ECUs? Just seems like controlling boost should not be as hard as it seems to be for you...(I am thinking better boost controller, and/or wastegate) Regards, Carl

AdrianE

I have the same problem as RX_Heaven because my boost controller (supposedly a very good one - Blitz SBC-iD) sometimes decides to let the boost build up to 15-20psi when I have set it to limit boost to 10psi! I'm not sure why it does this, but the Boost Cut on the LT8 I'm using is supposed to cut at 13psi and is too slow to react. So I have the fuel settings at 13psi+ up a little higher to make sure it gets overfuelled here (without pumping a silly amount of fuel in).

I'll start running 13-14psi when I get my E11v2 in a few days (tuning without WB logging is tricky, ATM I only have a WB display stuck on the dash!). But what are the main causes of these glitches in the boost controller. I had it installed with the boost pipe joining just before the (FMIC) intercooler, the other end goes to the wastegate. Is this right?

Adrian

RETed

If the EBC is working properly, typical problems associated with overboosting...
vacuum hoses too long
vacuum hoses too small
obstruction in the vacuum system
source vacuum point too far away from turbo

Let's look at the last point.
Are you saying your boost source point is all the way in front of the car?
Try to source a point as close to the turbo (compressor) as possible - this will allow for the fastest response from the boost controller.


-Ted

GUITARJUNKIE28

adrian,
i'm not familiar with that boost controller, but do you have to put the duty cycle in it yourself? if that's the case, maybe it's just a little too high.

RX-Heven

iTrader: (1)

Carl, originally I was taking all my vacuum/pressure sources from the uim. That combined with the fact that my vacuum lines were too long caused a delay with the ebc and hence my boost stability issues.
I did what Steve recommended and the problem was cured. I removed the compressor housing and tapped a vacuum source into the outlet just before the first coupler for the ic piping, hence as close to the turbo as possible. I also re-routed the vacuum lines to keep them as short as possible.

If you take the pressure source after the ic, the pressure would be lower if anything due to pressure drop through the ic. That also leaves a little room for error.

Indy cars pop-off valves are probably not 'off the shelf' units and are most likely adjusted off the car in a simulated system. Most of us do not have set-ups or the budget to dial them in like that.

I use a GReddy Type R wastegate and a profec b spec II.
I was not having any stability or spiking issues after I changed the source and routing. I am only looking to safeguard as a last ditch effort for any future mishaps.

My motor popped at mid boost and between 4k-5k rpm at part throttle with 96 octane and more than 3/4 tank of gas. My ebc showed the highest boost achieved was only 14.7 psi.
Still don't know why it went except it probably had something to do with the oil temps. 240' in the pan is high, but acceptable. I saw 260' briefly.

setzep

What were the intake temps?

Carl Byck

At the least, I would measure the boost at both locations so you know what you are really boosting. You will be adding fuel for "x" psi, while the motor is really seeing "x"- pressure drop. As far as a "delay, yes the ebc will react sooner, but that means you are not realizing the boost (at the motor) that you are setting the EBC for. It will also cause you to not be able to hold peak boost for as long, as you are preventing the EBC from seeing any losses in your system, and bleeding off boost prematurely. These losses, and shortcomings in compressor efficency change as boost goes up, so you really will not know what is going on unless you measure boost via a seperate gauge at the UIM. I still have never heard an explanation of how measuring off the UIM could cause instability of an EBC. As far as long Vac lines, I would move my solenoid closer to my vacume source. I just think that it is critical for all the electronics(EBC, Haltech) and accesories(FPR) to be reading the same boost pressures.

If you add a second FC cooler in series, and cantilever your hood(track only if you wish), you will solve your oil heating problem. Is your turbo water cooled? If the system is set up right you should see roughly equal oil, and water temps during extended full load situations(road racing). regards, Carl

RETed

I dunno about "instability", but it does affect the way the boost controller reacts.
I got to mess with theory recently when I had to tune a car that had not enough boost with an unmolested wastegate.
Stock, the turbo only managed to run 2.5psi on the boost gauge.
Haltech concurred with that reading.
With an A'PEXi AVC-R, we could only get the boost to hit a maximum 10.5psi.
Vacuum fitting was originally taken off the turbo compressor housing.
By moving this fitting to the intake manifold, base boost levels jumped from 2.5psi to 4.5psi.
The AVC-R also showed there was a massive spike when the boost initially rose.
It's funny though - even with the jump in base boost levels, we could only get 11.5psi of boost from the AVC-R at max duty cycle (91%).
We eventually figured out that the exhaust was too small (2.5" single)...



-Ted

Andrew

iTrader: (1)

It may have been, but it wasn't intended for boost control, it was used for the same purpose as restrictor plates on NASCAR engines, to limit power. Anyhow, I wouldn't use this method as my primary boost control, rather, I'd setup the Haltech to use a boost control soleniod.

setzep

Series? Woulden't that add a lot of pressure drop to the system? I would think parallel would be better because it would actually reduce pressure drop from the factory setup.

Carl Byck

That recomendation was suggested due to its simplicity, as he had indicated that he did not really want to mess with his system. I run mine in series with no ill effect. I agree with your thought, but have not found it to be neccessary.
Andrew, we are talking about a saftey net, not a means of boost control. My personal experience has been that a quality controller with a properly sized Wg is predictable. I say predictable, not stable. For example, if you set your boost controller to reach, and hold a particular boost in say third gear, pulling from ~3000 rpm on a 75 degree day, and then do a fourth gear pull from 2000rpm on a 40 degree day, your boost controller will most likely overshoot the target boost. This is why I like the AVCR, you can set different duty cycles, and boost levels by gear, and or RPM. this makes it alot easier to prevent overshoot. Also, since you can create two independent boost maps, you can have a cold weather setting, and a standard setting. Basicly a properly programmed AVCR can be set to apply a particular boost level, and duty cycle(gain) for each RPM range in each gear X two maps. Carl