i have seen you say this. are you sure? i thought it just retarded the timing when the knock sensor was trigggered. which fuel injection, early, late?

if wjm does not answer i will

 

i went 10 psi stock suby injection

to 10psi ms injection

and wow ..... yes more fuel does help infact i was a tiny bit rich in the top end and it would bogg down a bit

till ilifted

 

as soon as i get mine going again

i can give more infoe and even base fuel and ignition maps

 

10 psi althogh manged by saab 9000 apc turbo control's

10 psi boost stock mpfi versus 10 psi do it yerself or aftermarket injection setup's

either way for power/money and tunability i would go do.it.yerself. injection

that has a open code base that anyone can ad to or modify

 

oops nap time

i have seen you say this. are you sure? i thought it just retarded the timing when the knock sensor was trigggered. which fuel injection, early, late?

 

I thought it retarded it as well...but then i played with it some, purposely running too much timing...and I watched as unburned fuel exited the exhaust system and my fuel mileage went to 16 MPGs...then i tuned the timing back to where it was suppoed to be...and I was getting 23 or so...and no more fuel clouds!

 

Does the same on 85-86 as 87+...note: MPFI/TURBO only tho...as SPFI/CARB doesnt have a knock control system.

I thought it retarded it as well...but then i played with it some, purposely running too much timing...and I watched as unburned fuel exited the exhaust system and my fuel mileage went to 16 MPGs...then i tuned the timing back to where it was suppoed to be...and I was getting 23 or so...and no more fuel clouds!

 

Does the same on 85-86 as 87+...note: MPFI/TURBO only tho...as SPFI/CARB doesnt have a knock control system.

 

Maybe on 87+`s,but 83-86 engine computers have no input from the knock control system and therefore no way of knowing when detonation is occuring.

Maybe on 87+`s,but 83-86 engine computers have no input from the knock control system and therefore no way of knowing when detonation is occuring.

 

Yes it does. It dumps fuel at that point.

so whats the limiting factor on the 87+ systems. how much does it do it till. like if you ran normal timing and set it at 20lbs of boost. is the maf sensor the limiting factor? or the fuel pump, not putting out 20 extra lbs of fuel?

 

i would hope that the er27 responds the same way.

The advantage of the pre 87 is the fact ath you can disable the over boost fuel cut. 87+ its built into the MAF/ECU...and it will cut when 9 PSI or more is held for 10 seconds or so.

 

BUT...the 87+ has a better knock sensing system, better dizzy, and better ECU to handle the detonation issues when it arises...I have NEVER heard knock on an 87+....but even on STOCK pre 87s i hear it for a split second when turbo spools...then I see a slight fuel cloud. Timing retard/IC/better fuel cures that...but timing tuning is evAr so critical on the pre 87's its not fun at all.

 

87+...its still critical...but not quite as much...as the reaction and control of the knock is much much better.

 

I am going to install my GReddy EBC...and play with the fuel cut a little...at 10 psi only tho. Tune on some timing...and see how the engine does.

Oh, and the MAF is better than the flapper. HIgher air flow thru it...plus you dont have the spring loaded device to calibrate every so often cut you make changes to boost leves, intercoolers and so on and so forth...

Maybe on 87+`s,but 83-86 engine computers have no input from the knock control system and therefore no way of knowing when detonation is occuring.

i agree. the knock sensor is a stand alone unit, that retards the timing with vacc. the early ones relied on the maf almost totaly to know whats goin on.

i agree. the knock sensor is a stand alone unit, that retards the timing with vacc. the early ones relied on the maf almost totaly to know whats goin on.

 

the vac is advance only. None of the dizzys can retard either electronically or mechanically.

 

Both units dump fuel. 87+ is better at detecting it than 85-86.

the vac is advance only. None of the dizzys can retard either electronically or mechanically.

 

Both units dump fuel. 87+ is better at detecting it than 85-86.

 

You are wrong on all 3 counts my friend.

All pre 87 turbo distys retard both mechanicly and electronicly.

The "vacuum advance" also serves a pressure retard function.Take a look at the curves in your FSM.

They will all retard electronicly when the knock control unit says to.

Additionaly, they will all advance electronicly at high altitude.

 

Your unburnt fuel is due to something other than the computer responding to detonation.

Pre 87 engine computers can`t sense detonation directly and therefore can`t respond to it.

(prove me wrong by pointing out the pin#)

They will however enrichen the mixture when positive manifold pressure is sensed or the "full" contacts are closed in the tps.

the 85 to 86 is just a carb disty, so it doesnt have any way of electronicaly retarding the spark. its all centrifical, and vac. i think the knock sensor on old ones, just gave the disty some vac, when it knocked, which just reduced the advance, to somewhere near idle.

the 85 to 86 is just a carb disty, so it doesnt have any way of electronicaly retarding the spark. its all centrifical, and vac. i think the knock sensor on old ones, just gave the disty some vac, when it knocked, which just reduced the advance, to somewhere near idle.

 

Applying vacuum while knocking would advance the spark not retard it.

 

Knock control units are electronic.That`s why turbo ignition modules have 4 terminals instead of the normal 2.One of the extras is a phase control signal wire from the KCU.

The dizzy cannot retard. Only advance (vac for carbed/85-86MPFI/TURBO). The 87+ dont even advance.

The dizzy cannot retard. Only advance (vac for carbed/85-86MPFI/TURBO). The 87+ dont even advance.

 

 

So how does the knock control unit work then?

So how does the knock control unit work then?

 

Increases fuel upon detection of knock.

Increases fuel upon detection of knock.

 

Not what my FSM says.

Take a look at the attached scan of the knock control unit.

There is no connection to the engine computer.

FSM goes on to detail how timing will be retarded up to 10 degrees w/heavy detonation.(in fact, it is part of troubleshooting the KCU)

wjm i hae to say it but your wrong

knock sense is only ignition related on any car

 

it hears knock it pull s back teh timing until it goes away

tehn waits x amount of time and readvances

unless it hears knok again

 

 

btw adding more fuel or in the case of teh stock ecu getting the correct amount of fuel in reduces detonation alot .. i know same boost level same timing amount go from stock ecu to ms controlled injection no knock

how does it do this then?

when you run lean it has a tendancy to detonate

mostly cause less fuel in the mix the faster what little fuel ignites

more fuel the intake charge is a bit cooler /denser/wetter if that how you want to think of it and the longer it overall takes to light off

at least thats how i have always understood it

and knowing for a fact that with everything else being the same

just adding more/close to correct amount of fuel i was able to run the exact same psi of boost and hear no detonation

 

for me its hard to explain perhaps if i was more able to express what i think in a better way it would mae sense

but

my mind is such a nightmare for me to untangle i dread what it would belike if i let it lose on the unsuspecting populace

I need to play with t3h dizzy and FSM and some wired to see if I have been....slain!

well - i know for a fact that when it senses knock, it pulls timing...

 

this could cause a cloud of smoke if theres alot of fuel going in the motor..

but it dosent richen up, just pulls the timing