Rebuilding a map but my FSE is a hindrance

[TLicense]

OK, I'm going to admit it.... since installing the AEM my car drives like shite.

 

I think there's some serious issues with the current map. Not least of all the fact that the ignition runs massively advanced for my mediocre boost levels. The fuelling is also all over the place. It's not mapped with boost compensation, and lord knows what other little gremlins lie in there. Again

 

Now I've had a kind offer from Dimitri to come and put a smile on my face, and he also said he would map my car too. Unfortunately his prices are a little rich for my money at the moment so I'm going to have to resort to downloading the free basemaps and modifying them to suit my car (Something that maybe I should have done from the start!)

 

Now the basemap I've downloaded is mapped using boost compensation. Excellent, will be very quick to sort all the fuelling out. However the issue I have is that my fuel regulator is currently a rising rate one. Which is the next item to be junked, for a bog standard 1:1 rate regulator.

 

In the mean time this means that the fuel modification curve, which without the FSE, would be lovely and linear, will be far from it. Which is a pain.

 

Basically I'll be adding too much fuel by the amount that my FSE increases the fuel rail pressure by over the boost pressure.

 

Now I think, the FSE increases boost by 1.7:1 when on boost, and just 1:1 when on vacuum. (ie when my inlet manifold is at 14.7 psi, my fuel rail is at the static pressure + (14.7*1.7)) There was a MASSIVE debate about this, but as usual, there was no conclusion and no final proof that it was 1.7, or 1.17.

 

What I'm intending to do is go through each +ve boost load site on my freshly downloaded map, and multiply the figure by 1/1.7. (If indeed 1.7 is the magic number!) Hopefully then when everything comes out in the wash, the amount of fuel let into each cylinder by the injectors will be the original amount that the ECU intended. Right? That way I can keep the fuel modification curve linear, and hopefully will endure less faffing about when it comes to fine tuning.

 

What are your thoughts?

[Guest Usmann A]

doesnt the boost comp mapping have to be a linear formula from vacuum to boost, if so, it will not be a linear compensation and the point of where you being to make boost from vacuum would be a problem no?

 

what you think tony? can you get it to work like this?

[SimonB]

It's not quite as simple as that. If you increase fuel pressure by 1.7 times say, you will not increase the amount of fuel being delivered by 1.7x, but by a smaller amount. I've got the calculation somewhere, lemme see, ah, found it:

 

The formula for the relative amount of fuel you get with changing pressures is this:-

 

sqrt((new pressure)/(old pressure)) * 100

 

So for 40psi over 36psi that would be sqrt(40/36)*100 = 105%.

 

So that's like having 5% bigger injectors. If you rearrange you can find out what pressure you need for a given increase in fueling:-

 

new pressure = (desired increase%/100)^2 * old pressure

 

For example if you wanted to make 440cc injectors look like 550cc ones you would need to raise the fuel pressure from 36 to 56psi, as 550/440 is a 125% increase in fuel and (125/100)^2 * 36 is 56.25.

 

I can't quite believe the FSE raises fuel pressure by 1.7x under boost though, that would make it run mad rich. I take it you have a non standard fuel rail or something, otherwise I have a spare stock fuel pressure reg if you want one.

[Guest Usmann A]

I agree with simon, its taken more as a ratio, 1:1 is more fuel than 1:1.7, think of it as CR, the smaller the number the biiger the chamber volume= equal-er amount of both, the larger the number the less chamber space.

[TLicense]

Arrghh, Yes Simon, of course your right. Didn't have my thinking head on there.

 

It's not really a problem thought as I can get the AEM software to calculate it all out for me.

 

The Fuel rail seems to have been adapted to take some kind of square adaptor? Not seen one like it before. IIRC it's got a flange and is bolted either side, but it's not square to the rail. I'll try and get a pic tomorrow.

 

Us,

 

I don't think it has to be linear. Looking at the boost comp trim, it seems you just add fuel as a multiplication of the amount in the main fuel map. It's not just a formula, but a table %age fuel increase against load. So I could leave the main fuel map alone and adjust this graph down by the same amount that I would decrease load sites in the main map. The calculated total injector open time will be the same.

[Guest Usmann A]

sorry tony, you are correct, my bad, cool i get you, find out the % difference in the current AFR and target and apply that to the comp trim instead of a new map? your choice ...

 

then either play with the throlle inj in the vac areas to get it to run a tad leaner down there?

 

why not just swap in a stock fpr and that way you got no pissing around todo, sometimes making stuff simpler works ...

 

 

good luck, let us know how you get along.

[Ian C]

If you searched turned up the same FSE valve discussion I think it did, you'll find a post from me quoting info off their site, here it is again:

 

This is FSE themselves. They say:

 

Supra Turbo 3.0i

05/93>

VK-384-TOY1-H

£98.00

 

"On acceleration from standstill the Power Boost Valve fuel pressure will increase at 1.7 times the standard rate."

 

They also sell a "FUEL INJECTION (ADJUSTABLE BASE PRESSURE) 1:1 REGULATOR" (http://www.fuelsystem.co.uk/regulators.htm) Interestingly their website offers it for £40, less than half the cost of an PBV. It's an entirely different bit of kit to the Power Boost Valve, it's just an FPR.

 

Random sales blurb from a.n.other tuning company:

http://www.rpw.com.au/Products/Fuel%20Products/FSE%20FPR%20units.htm

 

"On acceleration from standstill the Power Boost Valve fuel pressure will increase at 1.7 times the standard rate. This will produce a healthy, strong fuel mixture strength which will instantly improve the drivability of your vehicle"

 

" When you have done any turbo conversion or planning on doing so, the rising rate unit means it also increases fuel pressure an additional 1.7 psi for every 1 psi of boost. "

 

Incidentally I called Terry Huxley of FSE to verify this as well. The whole bloody point of an FSE valve is to get more fuel out of injectors too small for the job. They do this by massively increasing fuel pressure when on-boost. So if your static was 40psi, you should see 50psi at 10psi of boost, with the FSE you'll get 67psi. If you have the right injectors for the job, junk the wretched thing

 

And if you want a stock FPR I've got one kicking around that has just been tried on another Supra so I know it's in perfect working order, and won't cost you the £90 a new one costs...

 

-Ian

 

PS and junk the AEM, put a stocker back in, and fit an E-Manage lol

[Guest Usmann A]

so if the amount of air is kept a constant 1, then by having the 1.7, ians right, your pushing 1.7 times the amount of fuel for a same amount of air, ok thats me done, bin the little shit. muhahaha

[SimonB]

so if the amount of air is kept a constant 1, then by having the 1.7, ians right, your pushing 1.7 times the amount of fuel for a same amount of air, ok thats me done, bin the little shit. muhahaha

 

Actually about 1.5 times, see my post above, but yeah that's pretty rubbish. I knew there was a reason I bought an Aeromotive...

[Guest Terry S]

You know my thoughts on the FSE........

 

Tony I have a spare stock one too if needed, and Mig has the -6 Aeromotives sitting there if it helps.