MAF problems
 

Hello guys, first let me shortly intorduce myself and explain why I joined your forum. My nickname is Dutch MX5 and I'm from Holland (where the miata is badged MX5) I registered for a friend of mine because he's having issues with is turboed Miata. I myself don't drive a Miata but I tend to have a wee bit more knowledge of cars in general then my friend has. I must confess I know very little of Japanese cars and injection-engines. (I'm focused on twin carb set-ups mainly)

Let's talk tech:

I know very little about the precize parts and build-years but I figured out the most from the net. My friend bought a stock first generation MX5 with a 1.6 16v engine which he had drilled up to just about 1.9. And they put on a turbo, intercooler and the lot. But now he runs into the problem that the engine doesn't get the amount of air it should when hitting a certain amount of revs. The problem is the stock MAF. It's diameter is too small to get the right amount of air in.

Did any of you guys run into the same problem? and what to do too solve it?
In europe we had a mazda 626 with a 2.2 engine with also the L-jetronic system. Is this an option or does it have a too small diameter as well?

Thanks in advance.

An rx7 maf might help, but an engine management like the megasquirt that can delete the maf would be a better solution.
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The inner diameter of the AFM is not too small to let enough air into the engine.

Probably the right solution, but the EMU can delete the MAF and the 626 will allow more air if he doesn't want to go full replacement ECU.

What is he using now for engine management?

^ i was gonna start off by asking the full engine set up (details). Especially the engine management. Also how did you find out that the car not getting enough air.

Well, actually I don't know all of it yet, but I know the engine is enlarged to 1900 cc (including other pistons, rods and the lot) and it has a GReddy turbo form the US ebay with some diy piping, He runs a small intercooler, a blow-off valve and some larger injectors (don't know the type because I'm a mazda-illiterate :) Further it's stock as can be except for the fact he took out the airconditioning.

He and his pal thought they were nearly there and took it to a professional tuner to give let him fine-tune it on the dyno because the car held back when the revs hit about 4000 rpm in fourth gear. This guy discovered that I couldn't breathe enough due to the fact the MAF was too small.

Megasquirt is nice and all but my friend doesn't have the knowledge nor does any professional tuner in holland. Megasquirt isn't used on a large scale in Holland yet. So I think the best solution is to stick with the original concept as much as possible.

The ECU he's running now is the stock one from the original engine. The question arises if this ECU can correspond with the MAF from the 626 or from the rx7 for that matter. (rx7 also l-jetronic or doesn't this matter?)

Deleting the MAF is also fine as long as it can be done with his stock ECU.

And what is this EMU you're talking about? Same thing as the ECU/Computer?
My english tech-talk isn't quite up to date I'm affraid :noob:

http://www.boostedmiata.com/dynos/rx7_vs_oem.jpg

Two Questions:

Which run was using the stock AFM and which one was using the 30% larger RX7 AFM?

How did a 1.6L get bore out to a 1.9L?

^EMU= engine management unit. Well whats the boost set at? It just doesnt really make sense that the car not getting enought air. Could be to much fuel if the car having problems at high RPM or maybe you need to replace the MAF because it fucked up.

EMU=Emanage Ultimate

EMU = emanage ultimate from greddy.
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Thanks for thinking along!

At this moment I don't know the amount of boost he's running but I will ask him and get back to you on this one.
And you say it also might get to much fuel instead. Now this might be the issue since he has bigger injectors installed. He did this because in an earlier stage he had too little fuel. And as far as I can recall they tried to turn up the fuel pressure. I thought this failed and that's probably the reason why he installed the bigger injectors. BUT then again should the MAF or at least MAP sensor deal with this problem?

The 1.6 ltr turned into an almost 1.9 ltr (1895cc or something) by changing the bore-diameter. And it has new nikasil cylinder walls as far as I know. I'm was at least new to it because the engines of my interest are all solid blocks drilled to the right bore diameter. I might have a thing or two mixed up because this was all earlier then when he came to me for advice on the MAF problem at hand. The increase in cubic inches might also be a result of an other crackshaft/rods/pistons but in that case he didn't mention it.

AFM and MAF are interchangeble? If the RX7 runs a AFM we change it for a MAF because they work differently right?

EDIT: Oh and if this EMU is a part of GReddy's kit he surely doesn't have it. The kit consisted only of a turbo, tubing and a universal intercooler. Everything not specific for the miata.

no, the AFM and MAF are not interchangable. I'm really trying to suggest that it's not to blame. are you certain it wasn't a 1.8L to start with? the MAF is not even close to a restriction in any means of the definition.


now, look at my dyno charts and answer question one.

Sorry I'm being a complete newby here but I guess their output is about the same? There is probably two different colors on the chart but I can't see it due to my color-blindness :eek5:

So when we X out this possibility, the only thing left would be to go back to the stock injectors to see what happes or maybe look into the fact that the old MAF is possibly broken?

What you need to do is get EVERY detail about his setup. Post up his dyno charts with a/f readings and maybe some pics of said car, specifically of the engine. Then we may be able to help you figure out whats going on.
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Will do so but I'm affraid he hasn't got a printout of the dyno chart because the tuner-guy didn't complete the run because of this problem. He said it would be useless to complete the run because he couldn't fine-tune it anyway. Otherwise my friend had to pay the full session (which I guess he better could have done anyhow) I will talk to him and make him mail me some info and specs on the car.

Thanks for the tech support anyhow guys.

exactly. one pull was made using a stock AFM. the next using a larger RX7 AFM. no difference.

It's not the AFM/MAF.

most likely a fuel issue. did they get a wbo2 printout? need more details on the setup.

also, where are you (and/or your buddy) located? I need to check that out :)

Haha, another Dutchy in the house I see! I'm from Surhuisterveen/Friesland

Didn't talk to him yet but I was wrong about the injectors. Looked up an old post on a dutch forum and it said he still ran the stock injectors. My bad.. :noob:

Wow. If this is true that's some cutting edge stuff right there. Nikasil on aluminum cylinder walls? Makes me remember my 2-stroke days.

^ Well the 1.8 stock injectors are ok if your running 8psi (with an FMU and enough fuel pressure)* on the TD04H 15 g turbo.

Maybe you can have your buddy shoot you an email on a detailed set up.



*mod added for accuracy.