V-mount = overboosting
 

I finally semi-finished my v-mount setup. i also did the poormans non-sequential, battery relocation and rewired the fuel pump. I test drove the car tonight and it is overboosting, i hit 14psi and 17psi at one point. the car felt extremely fast but I am afraid of blowing either the turbos or motor.

I have highflow cat & resonator, downpipe, 3" catback exhaust, streetport, now a semifinished v-mount (i still have to make ducting and complete the intakes).

i thought overboosting only occurs with straight midpipes. are my only options restrictor plates or porting the wastegate?

http://img.photobucket.com/albums/v7...d/IMG_6126.jpg

Porting the Wastegate would be a very good idea.

I did not experience any boost creep or spiking when I installed my VMIC, however I already had free flowing exhaust, adequate boost control, and tuning for the higher boost levels.

I *did* however notice an increase in boost when I originally went from my stock IC to my Greddy SMIC.

what are you running for a boost controller? I recently got an AEM tru-boost gauge. I am hoping that can help.

before i installed the vmount and non sequential i never had a problem with boost creep. I have not heard of anyone overboosting after doing a vmount. thats why im so worried.

thanks for the advice.

what do you have for boost controller? are you running stock fuel system?

That's a lot of mods without having a boost controller(sounds like you dont have one), what are you doing for engine management?

as of right now its stock.

i have a PFC and AEM tru-boost gauge with boost controller that i still have to install and tune.

If you want to play safe, have control over your car, and get good advice when problems like this happen, you should first:

1. Install the PFC
2. Install a WB AFR monitor with 0-5 V output for data logging
3. Install a Datalogit for data logging and PFC programming
4. Join Chuck Westbrook Yahoo group https://www.rx7club.com/power-fc-forum-47/subscribers-cewrx7r1-pfc-dl-tuning-notes-744587/

- Sandro

Excellent advice. At a minimum you need the Power FC and boost controller ASAP. If you plan to do your own tuning, then items 2 and 3 apply (although they're probably a good idea as well). I'd get these items installed and have it professionally tuned (or see step 4) before boosting it that hard again, or you're likely to have a huge (BOOM) repair bill.

your probably overboosting because of the Non-Sequential setup.. easiest fix is to get an EBC (or install the one you have)

my setup (non-sequential, cat-back, dp, larger SMIC) was boosting at 15psi.. just get an EBC.

If he installs the PFC, it does not need a separate EBC.

And the AEM tru-boost is not the best EBC on the market I heard - does not use pressure feedback I understand.

Check arghx threads on boost control, and also mine if you like. I use the PFC to drive 3-way valves, incidentally exactly the same valve as in the AEM kit, but at a fraction of the cost. Besides, with the PFC you can control PC actuator and WG actuator independently, which is relevant for those who appreciate the performance advantage of keeping the sequential twin control. No EBC allow you to that - unless of course you buy two.

- Sandro

Using the inherent boost control in the PFC won't replace a quality, dedicated, EBC... it's simply a band-aid.

I do agree that he should NOT be adding that many mods with a stock ECU though, that's no bueno. What I'm shocked by is how he's managed to avoid fuel cut so far... and IIRC the stock fuel setup hits 100% at around 13psi

I'm using the (Greddy) Profec B - Spec II EBC and it works like a champ.



I would HIGHLY suggest the OP do a LOT more research before pushing any further ahead. These cars show very little sympathy for poorly planned modifications.

Wait.. are you experiencing boost spikes or boost creep??? Boost controllers will help with spiking, but cannot prevent creep. Porting your wastegate can significantly reduce boost creep.

++++1

and install the boost controller as well ASAP. dont drive your car hard in this cold weather or is going to go KABOOM!

For the time being, remove the boost restrictor pill going from the primary intake compressor housing to the wastegate actuator. Just put a new silicon hose in its place and remove the factory line with the restrictor in it, should keep boost around 9-11 psi.

The stock fuel system can provide plenty of fuel at high psi. It just cant do it at high rpm. I think it may be impossible to hit fuel cut under 5K.

I'm not saying the OP is safe where he is. His car certainly needs some changes. I'm just making a point.

I must disagree Adam. I remember regularly hitting 100% IDC on my stock fueling for the short duration when I was boosting .85bar prior to having my 044 pump, FPR, and 4x 850cc's installed.

Granted, I never tested the fueling on stock ECU theory out myself... however I'm pretty sure I remember seeing a chart showing fuel cut based off RPM and PSI. IIRC 11.5psi, at low rpm, was the highest it went.

I could totally be wrong though.

Myself and Sandro have both done extensive testing and logging of the PFC boost control for both twin and single turbo applications. It's better than you think, it just took a while for people to really figure it out.

There are tradeoffs in any purchasing decision. I guess the advantage of the Tru Boost is its compact gauge design and low cost compared to other dedicated external EBC's. The disadvantage is a lack of feedback/gain control. The advantage of the Spec II is the relatively precise control it offers, while the disadvantage is the high cost, extra wiring/plumbing/clutter, and lack of logging capability. If you have a Datalogit PFC boost control is actually cheapest, it's definitely the cleanest to install, and it is integrated with the rest of your engine management. The instructions supplied by Apex'i are lacking however, so you're forced to learn how to use it from these forums.

The Spec II has gain control/feedback, the AEM Tru Boost does not. The Tru Boost is just a dumb solenoid driver. It has the equivalent of the Spec II's "SET" function (basic solenoid duty cycle), and START BOOST/SET GAIN function (pressure at which the wastegate cracks open, called "spring" on the AEM Tru Boost). What it does not have is an equivalent to the Spec II's "GAIN" which is used to keep the boost consistent through duty cycle self-correction.

The PFC has all those capabilities, but doesn't allow you to adjust the control logic as precisely as the Spec II. The main advantage of PFC boost control is full integration with the rest of your engine management. It lets you log the exact solenoid duty cycle through the Datalogit. This can be very useful for troubleshooting. You can switch between low and high boost settings on the commander instead of having an external box. And the boost control runs off the same MAP sensor as the rest of your engine management, so you don't have yet another display disagreeing with everything else.

You can control boost with the PFC and still ditch the restrictor pills and factory solenoids for only a small cost. Sandro, Dudemaan, and myself figured this out recently. Dudemaan found the AEM solenoid direct from the actual manufacturer (MAC) for cheap. For a plug-and-play installation I found both electrical connectors used on the wastegate/precontrol solenoids. Sandro did the back-to-back testing of the AEM 3 port solenoid vs the stock 2 port.

I am using the PFC to control my single turbo T04R setup right now. I've used it on sequential setups. Non sequential control is not a big deal if you have a Datalogit.

It probably does need more exhaust restriction or a higher flowing wastegate to control creep. Careful logging will be able to confirm this.

Still, it may not be enough if he goes too heavy on the throttle. This is a test I made, with the WG solenoid electrically disconnected (i.e. no air bled from the actuator) and line from compressor to WG actuator without pill.

Unported WG, stock twins, unported motor, DP, midpipe and dual N1 exhaust
2ng gear pull, full throttle

The third chart shows boost (“PIM” in PFC language) and ignition advance of the leading spark. The PIM in my PFC are rescaled as follows. PIM 10000 equals to approx. 0 psi (relative), PIM 15000 = a little less of 7.5 psi, and PIM 20000 = 14.75 psi

Before transition, boost stays just above the 7 psi WG spring pressure. After transition, boost increases linearly as the WG keeps opening. At 7000 rpm, my safety row is hit [I purposely pull ignition advance to stop boost creep]. In this test, boost creep up to over 17 psi.

https://www.rx7club.com/attachment.p...1&d=1258924248

Manual boost control with fully ported wastegate and manifold is the only way to fly with the twins. I have rock solid boost control at 15-16 psi. Don't rely on the PFC or electronic gadgetry, keep it simple....and delete all superfluous sequential nonsense.

Mark, I don't deny that MBC's work, work well, and work effectively.

However you cannot, honestly, speak poorly of "electronic gadgetry" when it comes to these cars.

Why downplay the ability to seamlessly limit boost at 10psi for regular driving then, without skipping a beat, shift up to 16 or 18psi at the press of a button when you want that extra power immediately (not later, after you've pulled over, popped the hood, changed some settings and gotten back on the road. At that point the moment has passed, and any power-plays are simply empty postures to convince yourself of your own superiority..)

If you routinely make dramatic shifts in boost setting, the electronic alternative has it's advantages. I always run pump gas, so I like to stay south of 17 psi. The only time I tweak boost is for ambient temp fluctuations, and MBCs work fine for that purpose. I also like to keep the cockpit uncluttered with various pods, gadgets, etc; it's just too ricey.

Ive ran the stock twins, full non-sequential, with full exhaust on over 40 different fds and the boost stayed below 11lbs. I dont mess with sequential too often but the few times I have and removed the restrictor going to the wastegate and precontrol I would occasionally see a spike above 10psi after transition but it would quickly drop back to 8-10psi. This is just my experience.

Well, my experience is limited to my own car. I hope that would not make you consider my logs as statistically irrelevant for that :)

The only thing I may add is that I had R-compound tires, had full traction/load and it was a quite extensive, hard full throttle application, for 4+ sec

Maybe my WG flap does not open completely, that I don't know. But I tested the actuator with a Myvac and saw the rod starts moving at 7 psi and stops at below 15, and these are pressure at the actuator, equal to the compressor outlet, not at the [lower] intake manifold pressure, as logged. Turbos are still original, never opened or adjusted otherwise.

And you can clearly see from the charts that the boost creep is stopped at 17+ psi by the IGL beeing pulled down to 4 deg, more than anything else.

- Sandro

I will try this but I will be installing the PFC and maybe install a manual boot controller to be sure.

I know I was both creeping and spiking, I also hit fuel cut *yikes*. so i probably will not be driving the car untill I get a full tune and a boost controller.

thank you everyone for your input I shall take them into consideration.

A manual boost controller cant help you any more than what I suggested. It will help you dial in a higher setting and hold it, but it will not make it boost less than I suggested. What I suggested makes the car run off the wastegate "spring"(actuator) and allows as little boost as possible. If it still boost creeps after doing what I suggested you need to port the wastegate.