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ApexDrift
08-21-2004, 01:25 PM
how can i be over boosting when fuel cut is at 8.5PSI, but my boost guage is reading 10PSI...

buh_buh
08-21-2004, 01:36 PM
your boost gauge could be off.
Are you using an Autometer?

EK 2.0
08-21-2004, 01:41 PM
As well as where you have your Boost Meter tapped could also be reading 10psi, but as far as your ecu and what it reads, its "tap" might only be reading 7psi for example

rage2
08-21-2004, 02:21 PM
Because you're in Calgary. Your ECU fuel cut reads absolute pressure, and your boost gauge reads relative pressure. In Calgary, your relative pressure will show 2-3psi higher than absolute pressure because of our elevation.

badseed
08-21-2004, 03:03 PM
:werd:

SwitchBlade
08-21-2004, 03:10 PM
It wouldnt be boost creep would it?

ApexDrift
08-22-2004, 12:11 PM
well i think the problem is a mix of boost creeping, boost spiking, and leaning out... cause every time i hit 6000rpm it hesitates, so im going to upgrade my secondary's, upgrade the fuel pump, port the waste gate, put in a FCD and that should solve the problem... but if that dont work im really confused

rage2
08-22-2004, 06:48 PM
Originally posted by ApexDrift
well i think the problem is a mix of boost creeping, boost spiking, and leaning out... cause every time i hit 6000rpm it hesitates, so im going to upgrade my secondary's, upgrade the fuel pump, port the waste gate, put in a FCD and that should solve the problem... but if that dont work im really confused
You sure that's not the rev limiter? ;)

Go4Long
08-22-2004, 07:15 PM
lol rage...it's a rotary...the red line is 7k and they go right past that...
yes...with that exhaust system it is all about boost creep, the exhaust will allow it to flow to much air, you are running an S4 wastegate right? which if I remember correctly doesn't allow for as much air flow as the S5's do...
your fuel cuts to the rear rotor at 8.5 psi...if you are seeing spikes past that you are leaning out the rear rotor(it still allows fuel to the front)
weird to see a hesitation at that high though...a lot of dyno graphs that I have seen on rotaries show the 3800RPM hesitation when the secondary injectors stage...according to what I was told in another thread the HT-18S runs out of steam at around 5500 rpm though...you might be seeing issues related to that...

ApexDrift
08-25-2004, 04:35 PM
the reason why the hesitation is so high is because my secondarys are maxed thats why i need a bigger fuel pump and larger secondarys... not to sure though got to bring my car in to JP and take a look:dunno:

Go4Long
08-25-2004, 05:09 PM
hmm...I have a set of 1000CC high impedence injectors for sale...but you are S4 right? I also have a set of low impedence 720's...they should be able to keep up with what you are running right now...pm me

Chris Ng
08-25-2004, 05:49 PM
I'm willing to bet that the 6000 rpm stumble would be due to missfireing igntion, rather than a fuel related issue.. are your plug wires still the stock ngk wires (they have blue boots) and what kind of shape are the plugs in? Replace your sparkplugs and wires and your will probably get rid of the 6000 rpm problem..
If you don't plan on raising the boost any higher than what you are running now but want a bit more safety, get yourself an FD fuel pump, or walbro and rewire the fuelpump to get 12V all the time... the stock 550's should be enough to handle your 10psi spikes, and the extra flow of the FD/walbro pump will overcome the stock FPR and raise your fuel pressure enough to keep you running rich.. mind you this will mena you will be running rich throughout your whole rpm band, but won't effect driveability too much.. If you go with the 720's in the secondaries, without any method of controlling them (ie: s-afc), you definitly will run too rich on boost, which will actually bring power down..

Just my 2 cents...

B18C
08-25-2004, 07:10 PM
Originally posted by rage2
Because you're in Calgary. Your ECU fuel cut reads absolute pressure, and your boost gauge reads relative pressure. In Calgary, your relative pressure will show 2-3psi higher than absolute pressure because of our elevation.

Can you explain this relative vs. absolute pressure thing? I don't really understand the difference.

Sorry for highjacking your thread :)

shadow
09-06-2004, 09:57 PM
I think you are ok.. I am running a 88 rx-7 and I have the same thing I put in a manual boost controller and it goes up to about 10 P.S.I on a regular basis. Although it would not hurt to get a fuel cut defencer or a eliminator.

Alpine Autowerks
09-12-2004, 07:33 AM
relative sensors measure the diferance between outside air pressure and manifold vacuum/boost. it is blind to changes in altitude & weather. manual boost controllers also fit into ths catagory.

absolute pressure sensors have a sealed referance (vacuum is sealed inside a chamber) and are able to detect changes in outside air pressure. this allows the boost control to compensate for altitude.

A turbo charged airplane (cars too) will loose power with elevation similar to a NA engined plane unless the waste has a absolute pressure reference in it's control system.