To MAF or Not To MAF

[99PBATR]

Hmmm I need a bit of advice. I am a new HSV Monaro owner and I have had some interesting advice on here. I have an 06 plate HSV Monaro with a Harrop HH12 supercharger and intercooler. One of the previous owners at some point clearly must have deleted the MAFF as the dyno plot suggests a MAFless tune.

Here is the thing though....the car when I bought it definitely had and still has a MAF fitted...but all is not well as it seems to have a slight misfire and is not good at all from cold. Having stuck an OBD tool on it, its reading a fault with the airflow suggesting the airtemp is very high and dense, which I was wondering if is caused by the MAF on it.

It was suggested to me that I should do away with the MAF as these are often deleted on supercharged cars. What therefore goes in it's place in the tube between the throttle body and the air filter? What are the consequences of dumping the MAF and if it is to be deleted, why would someone go and get one fitted to it again?

I am a little confused so advice would be appreciated all

[Yanayaya]

My Monaro is supercharged and my MAF gave me no end of trouble. The disagreement between the MAF, MAP, and Throttle caused the car to break down a lot. In the end, I gave up, went mafless and installed a 2bar MAP sensor. Even though I'm mafless the MAF is there in the pipe work simply because I have nothing to bridge the gap right now, it's just unplugged.

[Jader1973]

Surely the point of the MAFless tune is to allow the MAF to be removed because it creates a restriction in the intake?

Has your car had an OTR, or some other aftermarket intake, fitted at some point and then removed and the stock intake put back? In Australia OTRs shouldn't pass Roadworthy inspections so people put the stock stuff back to get the cars through when they sell them.

[99PBATR]

Cheers for the replies. Mine is fitted with an aftermarket K&N huge cone filter, which sits inside a custom made housing inside the left front engine bay to the front of the car.

It says in one of the invoices I have that its a Wortec CAI but after investigation the pipe leading from the throttle valve appears to be made by Harrop, as I contacted them and it looks the same as one of theirs. Needs replacing as its a bit old and slightly perished due to the heat. A new one is £200 from Harrop

Can't say i'm particularly impressed with it, as it seems to be a bit cobbled together. So if I read previous comments right, it would be best to disconnect the MAF or at least unclip the sensor wiring which is currently plugged in? Issue is that whilst it has been clearly mapped in the past, whether it has been mapped since to take the MAF is something I am unsure of. If I remove the MAF will it not play havoc with the airflow that the engine sees and cause issues? To be fair it seems to run crap from cold and has a slight misfire, which I am wondering if is caused by the MAF. I guess I can disconnect it and see how the engine runs without it? I can only assume someone stuck MAF on to get through a MOT for emissions. It's in at Walkinshaws in 3 weeks for a health check and a really good once over but the misfire is really bugging me.

[SturdyHSV]

Without the MAF connected the ECU will run based on the tables in the tune, MAP sensor, throttle position etc. It'll be fine basically, although it may expose weaknesses in the tune from a drivability perspective, as the MAF tends to help smooth over big airflow changes (think on / off idle, stamping on the throttle etc.)

You can map the MAF out I believe (haven't looked in a long time), and could just be using it as an intake air temperature sensor.

It isn't really much of a restriction from what I've read, I wouldn't say something worth worrying about on a car that probably makes over 500bhp, unless you are in to dyno numbers competitively or something

[99PBATR]

Cheers for the advice. Personally I couldn't give a fig about dyno numbers. According to the dyno plot I have that came with the car it managed 578BHP with a mafless tune. I will disconnect the MAF later and see what difference it makes to things. All being well it will improve my misfire....let's wait and see

[99PBATR]

Well that didn't go as planned. I disconnected the sensor wire and connector from the MAF and immediately the engine coughed almost died and then came back but with the engine warning light symbol and buzzer and the screen reading TRAC? Im not sure why this would come up but I assume that has nothing to do with the traction control. I can't see how it could. I'm just not used to this car so sorry if I sound dumb...every day is a school day

[anonymous-user]

If you don’t know what you are doing, you could speak to Paul from Wortec. He also maps cars for TopCats who do a lot of LS conversions for TVRs. They are based in Aylesbury so if you can get it down there I’m sure they will diagnose and fix the problem for you. Ask for Warren, he owns TopCats.

Edited by anonymous-user on Thursday 13th September 18:12

[99PBATR]

Cheers fella for the recommendation...it's in at Walkinshaws at the start of next month, so I'm hoping they can tell me all it's faults and we can start correcting them..I feel an anaemic wallet coming on

[Jader1973]

Sounds like it doesn’t have a MAFless tune if it won’t run without the MAF connected.

I did a bit of searching online and found a post that mentions having a TRAC error being traced back to a MAF fault, which was actually a split intake hose.

[99PBATR]

Nice one. I have never been too impressed with the crappy CAI pipework on mine and I did also wonder if there was an air leak in the system somewhere, which will throw everything out.

I also suspect it was a MAFless tune but perhaps now isn't. Now try and explain this one..I put a brand new MAF on it sometime ago and it would not hardly run at allSupercharger was having none of it and car backfired terrible...So I can only assume it's been mapped somehow to the current MAF and that has been modded in some way. The new MAF was a genuine LS2 MAF

[Jader1973]

99PBATR said:

Nice one. I have never been too impressed with the crappy CAI pipework on mine and I did also wonder if there was an air leak in the system somewhere, which will throw everything out.

I also suspect it was a MAFless tune but perhaps now isn't. Now try and explain this one..I put a brand new MAF on it sometime ago and it would not hardly run at allSupercharger was having none of it and car backfired terrible...So I can only assume it's been mapped somehow to the current MAF and that has been modded in some way. The new MAF was a genuine LS2 MAF

Based on a bit of digging I suspect the MAF that works with the supercharger will be a high flow unit, or at least "tuned" to work with the charger. As such the standard LS2 MAF won't work.

I should add I'm basing all of this on internet searches (the Australian Commodore / HSV forums are full of info) - my ute didn't have a MAF when I got it, just a cheap looking OTR and some orange silicon pipe

[99PBATR]

My guess is that you are absolutely right. When I put a standard one on it, the car misfired and spluttered something chronic, leading me to believe you are bang on. My only guess is that I have a high flow MAF that was either mapped to my car for emissions and perhaps has gone faulty and/or there is an air leak somewhere in the CAI system causing a fault and the OBD to see too high an air temperature. This may or may not cause the ECU to be causing the engine to miss slightly...either that or I am talking total bollo* and its a problem coil pack perhaps on one of the cylinders.

In others experience what common faults cause the LS2 to miss most?

[monkfish1]

Its clearly not a MAFless tune.

But in your first post you said air intake temps were high (whatever you mean by high?)

The ait temp is not measured by the MAF on a Harrop (or shouldn't be). Sensor is in No1 intake runner.

[99PBATR]

Thanks for the reply. The air temp we were seeing was reading in excess of 70c and it was throwing up 4 fault codes when using the OBD tool, so our assumption was that this was not right.

The Dyno plot that came with the car notes a 1 BAR maff tune and a 2 BAR maffless tune. By the looks of it, it made approx. 540BHP @ 1BAR tune at approx. 6400RPM and 578BHP on the 2BAR maffless tune at 6300 RPM. Max torque was 518.5 FtLb

My guess is that based on what I have read that I have perhaps a modified MAF on mine to suit the supercharger? Problem is I don't know much about supercharged cars but I do know it's not running quite right. We will see what the guys at Walkinshaws say when it goes in. Just want to get it running as right as it can be.

Judging by the raft of receipts, Monkfish supplied a lot of the parts for the car inc the Harrop Supercharger as they did for most of the cars on this forum

Edited by 99PBATR on Friday 21st September 10:23

[anonymous-user]

99PBATR said:

T
Judging by the raft of receipts, Monkfish supplied a lot of the parts for the car inc the Harrop Supercharger as they did for most of the cars on this forum

Indeed. See the post above ^ he’s the man who supplied them.

[anonymous-user]

monkfish1 said:

Its clearly not a MAFless tune.

But in your first post you said air intake temps were high (whatever you mean by high?)

The ait temp is not measured by the MAF on a Harrop (or shouldn't be). Sensor is in No1 intake runner.

Come on Roger, time to get the spanners out. We’ve missed you and it’s just not the same without Monkfish!

[99PBATR]

wormus said:

Indeed. See the post above ^ he’s the man who supplied them.

I figured that might be the case....the clue being in the name