Cap's MAF mod with fuel pressure

lamcote · August 22, 2018, 12:05

An easy way to think about it is that if you just fitted yellow injectors and didn't touch the MAF you would obviously be running VERY rich, until the fuel trims catch up and get it back to stoichiometric, because you have simply fitted bigger injectors. You would therefore get a LTFT of maybe -ve 25? Because the ECU would be pulling fuel based on the O2 sensors rich readings in the STFT.

Raising the MAF will progressively reduce this LTFT negativity by reducing the over fueling created by the yellow injectors.

So you just need to raise the MAF until you reach the point when you are happy with the resulting LTFT. Although if you go much below Cap's -7 you will be in uncharted territory so beware!

Optimus prime · August 22, 2018, 16:55

thanks, that's a brilliant way of looking at!

lamcote · August 24, 2018, 02:55

Quote from: Optimus prime on August 21, 2018, 19:36
Ive found someone who will be able to machine a plastic spacer. Question is, how high should I make it? I will get a couple done so i'm happy to try a range of heights.

If you get this working will you be able to make some available to buy for the rest of us by any chance?

Optimus prime · August 24, 2018, 15:40

I will get this up and running first. I have 4 different sizes coming next week so I will have a play and keep you updated. how many people would be interested in a MAF riser?

lamcote · August 24, 2018, 23:07

I could be tempted at the right price, it's something I have often wondered about doing as an experiment.

Optimus prime · September 2, 2018, 22:14

Just a quick message to let you know I did the MAF raiser along with Yellow 2ZZ injectors and I'm over the moon with the results. The car has a sudden urgency when you squeeze the throttle. Much more responsive and more punch through the rev range. It just keeps on pulling, i've accidentally hit the rev limiter a couple of times because it just feels like it wants more! Don't get me wrong, it's no Turbo but it's a brilliant mod that I'm really happy that I tried it; No money was wasted here (unlike my induction kit attempt). Engine note has also changed, I can't wait to slap on a cobra or TTE exhaust in the next couple of months!

lamcote · September 2, 2018, 22:44

Excellent, what height did you raise the MAF in the end?

Optimus prime · September 4, 2018, 07:24

I raised it 1/4" (6.35mm). I also have a spacer 1mm above and below that benchmark. I will re-read the LTFT soon and make a judgement on whether it needs adjusting. From my initial trials it seems bang on!
I had the ID of the riser made at 31mm. If I were to do it again I think I would get a 31.5mm ID as 31mm is really tight on the o-ring around the MAF.

shnazzle · September 4, 2018, 07:29

The engine note change is the timing adjustment the car makes. It's the first thing I noticed when I just put my map back on.

It's the poor man's piggyback ECU, the MAF mod. Clever stuff

lamcote · September 4, 2018, 09:03

Quote from: Optimus prime on September 4, 2018, 07:24
I raised it 1/4" (6.35mm). I also have a spacer 1mm above and below that benchmark. I will re-read the LTFT soon and make a judgement on whether it needs adjusting. From my initial trials it seems bang on!
I had the ID of the riser made at 31mm. If I were to do it again I think I would get a 31.5mm ID as 31mm is really tight on the o-ring around the MAF.

Is it a simple plastic ring? Where did you get it made, can I ask how much it cost? Cheers

Optimus prime · September 4, 2018, 09:37

I had mine made out of aluminium as it was easier for the guys to manufacturer but either plastic or metal are suitable.

I got mine done through a friend at a super buddy hug price of nothing.

It was done by a machining company with a CNC machine. I gave the ID, OD and thickness. That's all they needed and the result were perfect.

The company I used were EyeTech engineering but I would guess with a little google searching in your area you would find someone nearby. If you get stuck do give me a shout.

lamcote · September 4, 2018, 13:56

What OD is required? Otherwise it's 6.35mm thick and 31.5mm ID? No notch required for the MAF?

Optimus prime · September 5, 2018, 09:25

I went with a 37mm OD which was fine.

I didn't do a notch for the MAF as the ID of 31.5mm would clear the MAF sensor. unscrew your MAF and have a look at it, i really don't understand how/why people made notch's in theirs.

lamcote · September 5, 2018, 11:19

Excellent, thanks.

Optimus prime · September 10, 2018, 13:30

hey guys,

Quick update; I raised the MAF to 7.35mm and I lost the power I had before and the ECU was pulling more fuel (LTFT seen on attachment). I returned it back to 6.35mm and the power came back. I will do some more readings once the LTFT have levelled out, once I have those readings I will lower the height to 5.35mm and check the results.

I just wanted to highlight this as only 1mm had a big impact on performance

shnazzle · September 10, 2018, 13:55

Very interesting to see the results with the higher and lower MAF settings
Nicely done

furbern · September 14, 2018, 13:29

Good result! What fuel were you running on to see the improvements? Or to put it an other way do you need to use premium fuel?

Optimus prime · September 14, 2018, 15:43

I can safely use standard fuel in the UK but to my knowledge this wouldn't change LTFR's

Optimus prime · September 14, 2018, 15:47

Using 6.35mm spacer...

Fuel trims are reduced so the ECU is pulling less fuel but i think i might have a leak in fuel or air as the banks are reporting different results... see the scale of the fuel trims on the bottom right and left

Essex2Visuvesi · September 14, 2018, 16:15

Anyone have one of these to hand? thinking this is an ideal candidate for 3d printing

As the proud owner of a 3D printer I would be able to make them to any height required in steps of about 0.1mm

Optimus prime · September 17, 2018, 14:10

3D printing would definitely get you there. I installed the 5.35mm spacer today and it doesn't pull as hard as the 6.35mm spacer higher up the rev range. i'm just waiting on the LTFR's to settle before i post another result.

Optimus prime · September 20, 2018, 13:45

Hi Guys,

quick summary of my findings.

With the yellow injectors in, the vanes removed and the MAF raised different levels I found the following:

5.35 spacer: ECU pulled less fuel on the LTFT - Throttle response was good but power over 5000 RPM was lacking compared to the 6.35 spacer
6.35 spacer ('official' recommendation): - Throttle response is great and pulls a lot harder from 3000 RPM to redline (much improved over stock)
7.35 spacer: ECU pulled more fuel on the LTRT - Throttle response was poor (similar to stock) and the power was not comparable to either of the above.

My theory based on research of the Mod is; with the 5.35mm spacer timing is advanced but it's over fuelling at the top end causing it to 'slow down'. 7.35mm spacer has less advance and becomes more like stock. What i'm amazed at is that only 1mm has a huge impact on performance. What i have done here is nothing new but I found it interesting, it just puts my mind to rest that 6.35mm spacing is spot on.

the reasoning for trying the different spacers is because i removed the restrictive bend from the side hose to the air box and i wondered if this would have an impact on the MAF mod and the spacing... apparently not.

I'm so glad i did this mod, forget about figures and dyno's etc. it makes the car faster and more responsive, £60 well spent!