EdwardNorth

Hey all,

I've finally been able to start driving the 7 since winter is going going and gone! I've started testing it with my new DP and also the RB CB. I *do* also have a K&N air filter for the stock airbox but that's the extent of my mods. I noticed that in 2nd gear at WOT, I would boost around 10.5 to 11 after transition to the 2nd turbo. However, I did a 3rd gear pull on the freeway, and I noticed that I'd get about 11-12 psi on primary, and immediately after transition when the 2nd turbo came online, I'd be just slightly above 12 psi and it would drop a bit and stabilize between 11.5 and 12. I noticed that my trusty A/F ratio gauge showed solidly in the green, however. (I don't know what to make of that though since I see people here say that those gauges are worthless...).

After searching and reading some of the other threads, I'm a bit worried but still not 100% sure about this. On the stock ECU, is 12psi or slightly above for a moment after transition dangerous? Is this normal with one's only mods basically being DP and CB? I need to get new tires more than anything but until I either get a PFC or know for sure that 12 psi is OK on a stock ECU, I refuse to get on it at all (at least in 3rd gear, I imagine the PSI in 2nd is acceptable).

Thanks guys, I appreciate any input.

dubulup

12psi is pushing it...although people will tell you they've run 15psi no problem for years, blah blah...

If I were you and want to spend money on tires (instead of the PFC), I'd get a boost controller and limit the boost to 10 (or 11psi max). You should have hit fuel cut before 12.5psi...I can't remember what the rpm/boost - fuel cut table says but that's definitely walking a thin line with the stock ECU. Your plans for 2004 look great.

BTW, how'd she feel at those boost levels??

alberto_mg

Yeah, turbo rotaries build boost so easily once exhaust backpressure is decreased and intake enhanced. Thats why it is so tricky to "mod" turbo rotaries.

I'm with dubulup on this. If you wanna be safe, get a boost controller or get a M2 or PFS type ecu. They go pretty cheap used and will be easier/cheaper than installing a powerfc that will probably also need to be tuned in order to control boost properly. Then you should still have enough $$ for some tires

Good luck.

911GT2

I'd do the same. 12 psi is definitely pushing it on the stock ECU, even if it's only for a split second. Your ECU actually adds less fuel during transition, because it's expecting a dip in boost to about 8 psi, so you're pushing it even close to the limit than you may realize.

Boost controller at the very least, chipped ECU would be better, PFC is best.

EdwardNorth

Thanks for the replies.

Once I do end up getting the PFC, I thought that I read the base Mods program boost is set to about 11.5 PSI? I've been under the impression that the PFC should do a fine job of controlling boost and fuel (especially with my small amount of mods) right out of the box. Is this not correct?

I figure with the money I'd spend on a boost controller, I want to get a PFC anyway so I should just go for that straight away. I might even get a PFC first before new tires, but with them as bald as they are I STILL won't be able to get on it from a launching perspective anyway.

Oh, and I dunno how the boost really felt, I was too busy sweating when I saw the boost go to 12+ after transition!

Thanks guys!

dubulup

That statement sounds true. Some have had problems controlling boost, however they are probably more modified than you plan to go...but you never know, it's a sickness, hope you don't catch that bug

racer1

At least get a boost controller if you cannot afford a PFC for now and you'll be fine.

EdwardNorth

I've read that those with Midpipes have the most problems with boost control on the PFC. Most seem to agree that the base mods program though is good for intake, full exhaust, and intercooler at least. I figured next year when I look at an intercooler I'd also spring for a tuning session right after the install. For the time being though, I'll want to keep the boost at 12 PSI after the PFC goes in, so I guess it's time to learn all I can about duty cycles and all those other terms.

I'm such a n00b.

adam c

iTrader: (2)

Rynberg isn't here, so I will tell you to keep the boost to 10psi on the stock ECU (someone owes me a dollar) .

Since you are trying to save money for tires and a PFC, I suggest that you install a manual boost controller. It's cheap, works well, and is easy to install. You can easily remove it if you decide to upgrade to something else later on. Here's a link:

http://www.rx7turboturbo.com/robrobi...controller.htm

Do not install the prespool controller. If you want to upgrade your stock airbox, I sell a kit for $70. Here's another link:

https://www.rx7club.com/forum/showth...hreadid=121491

lopedl

iTrader: (1)

Yeah, I would definetly have to agree with what everyone is saying, a nominal fee for at least the boost controller is well worth it. I would definetly worry about the aftermarket ecu before the wheels, cuz if you chance it you'll be buying a new engine to complement your new wheels , bling, bling.

lopedl

iTrader: (1)

I mean tires bling bling.

Tad

yeah man,
you drive an FD,
time to start thinking like it.

dont go blowing your money on DUBZ when you have
engine management issues.

engine management issues leads to engine replacement issues.

RollnDrty

You can easily pick up a PFC up for sale in the classifieds section, the base maps will protect you, and you don't need the commander. I blew my first motor because I played by the 3-Mod Rule, had CB, DP, and Intake, boosted no more than 12lbs and lost all compression in a matter of a week.

FDjunkie

I'm in a similar situation in that following installation of my new catback about two months ago; I knew and planned to reduce the boost back down to near stock. My car is a one-owner daily driver with the stock ECU. However, while waiting on the weather I decided it was risky to depend only on the readings from my Defi mechanical boost gauge.

Long store made short is that I used my DIY compression tester https://www.rx7club.com/showthread.p...ression+tester with some modifications to log the attached boost pattern. I’m working on a write-up, but for now the resolution was +/- 0.25 PSI and 30 readings per second were logged.

My testing has convinced me that I could not reliably read my column-mounted boost gauge with any precision while driving at speed, and further that even a good gauge won't react fast enough to catch what's really happening.

I also discovered that I had an unknown boost leak after transition. A loose hose clamp on the charge relief valve accounted for about 1 PSI, but I'm still looking/testing because as you said, I too believe that my boost following transition should come close to the same 11~12 PSI.

EdwardNorth

I'm going to order the PFC in 2 or 3 weeks. I can probably swing both the PFC and the tires at the same time but if not, I'll just get the PFC. Until I get it I'll just avoid WOT like the plague.

Thanks for the replies.

MrRx

iTrader: (1)

I have the same basic mods and i run about 12-13 psi on my turbos, the crappy a/f gauge i have shows all green

911GT2

Thats because AFR gauges that use the stock O2 sensor are useless. Please don't trust that, and please get a boost controller to put that back down to 10 until you get some sort of engine management. You'll thank me later.

alberto_mg

Again, if you are on a budget keep an eye out for used M2, PFS or Pettit ECUs. I've seen them go for ~$400 and they will fit your need quite well.

As a PowerFC owner I know the PowerFC is "better" and more adjustable, but the other ECUs will do the job while controlling boost for a fraction of the cost and you don't have to worry about getting it professionally tuned.

mad_7tist

get a profec-b