FNM

Hello again

I'm just discussing on the UK forums that yesterday I took my car to be dyno'd (has HKS air filter and kakimoto r exhaust) and I was stuck at 0.5 of boost ( see here for the graph)

Now this guy I was talking to said his stuck at 0.5 boost when the engine was real hot (after traffic and so on) and that turning the engine on and off seemed to reset something in the engine...

following that I looked at my heating chart and it's showing an 87-87.85 degrees f so I dunno if this is the case?

anyone know anything like that?

thanks in advance!

Pwantwan

Sorry to go slightly off topic here, but where's this UK forum I've heard so many of you talk about?

Thanks,

Pwantwan.

fd3s_rx7

iTrader: (13)

hehe Hi dude, there's two UK rx7 clubs FDUK & where i'm asking more or less the same question at the moment... Mazdarotaryclub

Hope to see ya round soon!

Andy

p.s. I think this forum is screwed up as i've just posted under someone elses login (me being FNM)

FNM

hmm that's better

how odd!

911GT2

Your boost will be slightly lower in warmer temperatures, but it shouldn't stay at 7 psi. That suggests to me that one of the wastegate control solenoids is not working, so the wastegate is reverting to using it's own spring pressure to control the turbo boost, which is 7psi, which is just about .5 bar right? (1bar=14.7psi?)

Thats intake temps? Thats actually really low for intake temps, thats only like 25-30C which is the lowest readings I ever get with my stock IC on the Power FC. My stock twins can make 12psi with intake temps 50-60C, so those temps are fine.

FNM

oh I was told that 87 was pretty dam warm. The temp was around 50 degrees f that day I had it dyno'd so it was quite cold?

with regards to the solenoids, are there any easy way of checking these. Basically in this country none of the mazda garages touch rex's and the closest garage is miles away... dunno if theres anything I can do myself to check this out?

cheers bud

FNM

p.s. here's the temp chart

fd3typer2

Did this prob ever get fixed? I have the same problem at the moment!

I thought I would raise this old thread to save getting burnt for not searching etc.

RTS3GEN

Boost should default to spring pressure with a stock based ecu under 177-178 degrees' F, and over 242 degrees F. Pulls timing also.
Art

FDjunkie

It makes sense for the ecu to pull timing and reduce boost when the engine temp gets so hot, but I never thought about it reacting this way when the temp is just a little cool.

Is the ecu only looking at the water temp, or does the air temp play a role in this behavior, too?

Rayman93RX7

iTrader: (4)

I notace that on the dyno I have to raise the gain on my boost controller since the load on a dyno is different than the street. The stock FD boostcontroler is simply a basic on off vavle and a wastegate spring, non ajusting to what the map sensor is reading(other wise manual boost controllers wouldn't work on FDs) so it wouldn't ajust to the different load of the dyno, so I'm guessing it's cuz of the dyno assuming that you don't have the same problem on the street.

fd3typer2

I get the problem on the street not the dyno. Also, I have manual boost control and pre control, and I have bypassed both wastegate and pre control solenoids. I was getting the problem before I put in my boost control. I wanted to see if the poor transition I was getting was related.

Just to note, I did it like in this thread https://www.rx7club.com/showthread.p...=perfect+boost , and I had to cap the actuators. My results were:

No control - 12-11-14
2 controllers without actuators capped - 14-12-14
With actuators capped - 10-9-10 ( Or whatever I want to set it at)

The boost is now stable, quick and very smooth transition.

All the above is true, until I get this weird problem. After driving a bit hard, it seems to switch to 7-5-7, until it cools down and I KOKO.

I will be investigating the lines, check valves and solenoids some time soon. I wishI never sold my Mityvac after I sold my last FD. Damn they are expensive here in the UK.

I hope someone can point my in the right area to start checking.

RTS3GEN

Did you read my last post? Are you on a stock or remappped ecu? If so, this is your problem, I'd be checking my thermostat or cooling system for problems(ie too much coolant or warped caps that are letting the temp rise to much and too quickly).
Art

fd3typer2

RTS I read your post. At the moment the situation has changed. Now it is permanently at 7-5-7. I will check the cooling system for any faults.

The ECU is stock.

fd3typer2

I was thinking, even if the ecu wanted to leave boost control to spring pressure, shouldn't it still be above spring pressure because I have bypassed the solenoids and am relying solely on the valves for boost control?

RTS3GEN

Not necessarily, the timing gets so retarded that the turbos won't spool beyond spring pressure.