12-8-15 Boost pattern...
 

Well, my boost is back...had a bad boost leak(max 7 ....no secondary)

Anyways, the pattern seems to be pretty consistently now since I got it back this afternoon.
12-8-15(14)... [My boost control on the Profec B is at 3/4's].

The 15 does not suprise me given my mods but I was wondering what might lead to the asymmetry. Any ideas????

The nice thing is my A/F at 15psi (as measured on an FJO Wideband) is way rich...haven't had anything tuned yet since the rebuild and reconstruction but everything except sub 0 boost is in the 10's.

David

sorry....mods are in sig this time

Quite possibly boost creep. Is your wastegate ported?

Are you seeing any boost spike?

If no, have you considered a bit more prespool?

Boost Spike : Don't think so but I'm not quite sure I really know.

Considering Prespool : How would I change this anyways?

The boosting doesn't seem to be a problem, in fact I rarely am boosting unless trying. Laugh if you want, but it's taken all these years to just get a boost gauge so seeing these patterns is new in itself and I've had so many mods and no previous gauge so it's hard to compare now what is deviating.

My PowerFC shows a max duty cycle of 65% all day anut I'd my AF ratios seem way conservative under boost so it doesn't at least APPEAR to be a problem, but I want to understand what's going on.

Is your wastegate ported?

What does 12-8-15 someone please explain this.

It's a boost pattern, if you're not sure what I am refering too then
read all this..


https://www.rx7club.com/forum/showth...threadid=68640

really don't feel like reading alot. Would someone just simplify?

Don't feel like reading up on the 3rd gen but yet you're looking so hard to buy one?:confused: Get used to the reading buddy, because believe me if you get a FD there's alot of reading ahead of you, most of which *should* be done before you even think about getting one.

At any rate the FD uses a sequential TT system but you should already know that.

As per Scuderiaciriani... On a stock FD...

At 3,000 rpm you should get 10 psi
At 4,500 rpm as secondary turbo comes on you should get 8 psi
At 4,500+(almost immediatly) you should get 10 psi

And from 6,000+ on up you're supposed to get 8 psi but I don't think anyone ever either bothers to check boost at 6,000+ rpm or it goes too fast for them to get an accurate measurement so no one usually lists it.

Now normally people refer to a perfectly fine running FD's boost pattern as 10-8-10. DavidDeco's is 12-8-15, I *think* he's trying to figure out why the numbers are so different, another words getting 12 psi on the first turbo, 8 psi on the switchover and 15psi on the second turbo.

http://www.scuderiaciriani.com/rx7/boost_test.html

Sorry to whore a thread..

what's wrong with 12-8-15 though that's higher psi meaning more hp am i wrong? wouldn't like 12-10-12 be good?

Easy!!!!...DON'T BUY AN RX-7

OK, I have seen a big dip in transition mostly for two reasons:

1. Your Turbo Precontrol Valve is not opening early enough, meaning you are not getting sufficient prespool on the second turbo. When transition takes place, you see a big dip until the second turbo spools up. This can be fixed by installing a slightly larger pill oriface in the line to the Turbo Precontrol Actuator. BE CAREFUL! If your lack of prespool is due to a blown off hose/faulty actuator, then you could blow the engine when you get it all together correctly. Also, very little change in oriface size = a lot of change in prespool = potentially big spike. The reason I asked about boost spike was putting in a bigger pill will give you more of it. I would check the Turbo Precontrol Actuator, lines, and Turbo Precontrol Solenoid before making any changes to the pill size.

2. Your Turbo Control Actuator is not transistioning properly. Check both the pressure and vacuum sides of the actuator, including the actuator itself, lines, 2 solenoids, and of course the pressure/vacuum tanks and associated check valves. I had bad transition because of a bad check valve to the pressure tank. Only the vacuum side of the TCA was working.

Good luck. 15 lbs is a lot of boost.

Yeah, it's a pretty nice rush :D The mechanic had told me he was seeing around 14's now after finding the leak and a lot of reassembly. I got it back and drove it around checking some vital signs for an hour and then took it home. I finally got on a causeway where I thought I could let her rip a bit.

I'm going to experiement some more and check what you mentioned. I'm not too worried about the 15 itself because my Injector duty cycles have yet to break 70% still and the car is in the 10's at boost on A/F. I am very glad though that I splurged for the wideband now.

No its not ported but I though boost creep was only a big factor if you had a MP, I have a HF cat. However the more I looked at it today, the more it seems that is what it is.

My ProfecB seems irrelevant to all of this as well but I only had 1 hour of driving around to test it. Tomorrow I am going to find a nice area where I can do some runs and isolate some patterns.

black99, i admire your patience...