Severe Flat spot a short while after 360cc injectors install

neap38

neap38

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Just installed larger injectors into my AGU. Everything was running nice and smooth for a good few hundred miles/ few days until last night a severe flat spot problem occured.

Its still holding/creating boost fine during the flat spot but it has barely no power until it kind of splutters and jerks back into life again towards the top of the rev range.

Im really confused to what this might be?

Any ideas?

Also, are the 360cc red top injectors a straight swap?
 
you cant just fit larger injectors....

The ECU is programmed with the size of the injectors fitted, putting bigger ones in requires the ECU to be remapped accordingly.

Why have you fitted bigger injectors anyway?
 
aragorn said:
you cant just fit larger injectors....

The ECU is programmed with the size of the injectors fitted, putting bigger ones in requires the ECU to be remapped accordingly.

Why have you fitted bigger injectors anyway?
Click to expand...

To run along side extra boost (mbc) and a maf in vr6 housing.

It is also running a brand new factory dumpvalve.

Just stumped why it is running flat but the boost is still normal?

I was thinking it could be down to fuel starvation and possibly a dodgy fuel pump?
 
Probably because the map has no idea whats going on?

ME3.8 is as dumb as a dumb thing... its very limited in being able to handle stuff... its still load based so by fitting a larger MAF tube you have reduced the load values the ECU sees for the same amount of air... everything the ECU does is essentially determined by the load it sees from the MAF... by changing it to a larger tube and using an MBC you are trying to increase the performance beyond the limits set in the map and the maps limited protection routines are trying to fight back...

Without proper mapping to fix up the changes to airflow the ECU is now seeing its no wonder you are encountering flat spots here and there... its probably pulling loads of timing as the load sites it thinks its in is using higher timing advance than what the engine is actually able to use...

Have you tried logging it at all?

<tuffty/>
 
<tuffty/> said:
Probably because the map has no idea whats going on?

ME3.8 is as dumb as a dumb thing... its very limited in being able to handle stuff... its still load based so by fitting a larger MAF tube you have reduced the load values the ECU sees for the same amount of air... everything the ECU does is essentially determined by the load it sees from the MAF... by changing it to a larger tube and using an MBC you are trying to increase the performance beyond the limits set in the map and the maps limited protection routines are trying to fight back...

Without proper mapping to fix up the changes to airflow the ECU is now seeing its no wonder you are encountering flat spots here and there... its probably pulling loads of timing as the load sites it thinks its in is using higher timing advance than what the engine is actually able to use...

Have you tried logging it at all?

<tuffty/>
Click to expand...

I haven't had a chance to plug it in yet. That will be my job for tomorrow.

I understand what your saying and before I installed the injectors the other day, I was skeptical if it would run correctly or not... however, it did, it ran smoothly for a good few days and plenty of miles; and if I'm honest, I was having a bit too much fun thrashing it about and enjoying the pops and bangs and fire out of the exhaust (silly me). But this makes me wonder if it is actually the ECU seeing as the engine was coping fine.

I originally installed the injectors to solve the problem of my car Jerking under WOT once the engine had warmed up (choke off) which too seemed to be down to fuel starvation or such a lean mix, the added boost was putting the spark out?

My list of things in my head that I want to narrow down would be:

Possible fuel starvation ( dodgy pump)

Air in fuel line ( I have a slight fuel leak ("rain drop" every minute) just after the fuel filter.

Then possibly spark plugs/ coil packs but it doesnt feel like its misfireing... more as if there is a lack of fuel or air.

Please dont be offended by my lack of mechanical sympathy.

Your help is appreciated.

Thanks.
 
Also, is anyone clued up on knowing if the 360 redtop injectors are a straight swap on a AGU? They did fit fine however I can twist them slightly quite easily while they are in position and bolted in.
 
They aren't a straight swap as they are larger and not scaled... the map needs to be told about the larger MAF and the larger injectors

<tuffty/>
 
Okay tuffty, thanks for the reply. Physically, they are the same size though for mounting? Spacer aren't needed as far as im aware?
 
fortunately for you, once it's stopped bore washing the engine to oblivion you won't need to worry about flat spots.


There is more to tuning that adding boost/fuel otherwise mapping would be pointless.

Why not get the thing mapped/chipped properly, then it will be as good as it can be once you have fixed it's issue with flat spots. Which are more likely related to vacuum/pcv/boost leaks
 
Remapping is something id be interested in but at the moment, compared to the value of the car (£350) and the time I will be owning it for, It doesn't interest me enough at the moment. Where as I fully understand it is by far the preferred method, others have gone down the route I have taken with reasonable results and I'm more interested in sorting out this little gremlin thats occured.
 
Where you speak about the boost leak, it wouldn't really explain why I still have normal boost pressure yet the power temporarily changes would it? However, the pipes are all still original apart from a couple going to the intake manifold and to the new DV. I have also replaced the turbo a couple of weeks ago so other pipes have been interfered with recently which could back that up.
 
Ah you never mentioned the MAF in the first post. That changes things.

I'm running my Avant in a similar setup at the moment, Stock tune, C20let Yellows, 3" MAF housing, hybrid turbo.

It runs fine with only a small amount of fuel trim, the biggest issue is the ignition timing is somewhat over advanced, due to the ignition table being based on load, which is reading incorrectly due to the big maf. V-Power is a MUST, putting 95 octane fuel anywhere near it in that state would undoubtedly be a recipe for disaster.

Its a bodge, but its my only option at the moment as my turbos been upgraded and its off the end of the stock maf scale. I'm going to be getting mine tuned soon now that all the mods are in place.

I find mine is pretty flat below 3k, 3-4.5k is pretty decent then above 4.5k it seems to do a VTEC impression. All of this is due to the ignition timing being incorrect. I'm also running it on actuator pressure as the wastegate duty cycles are completely wrong for my turbo, but its a 12psi actuator so it works pretty well.



You really need to scan for codes and do some logging to see whats going on.
 
Really appreciate the help on here as always. I'll scan it tomorrow and ill see if anything pops up. Funny you should mention the V Power part, it was running on high octane until it almost hit the empty which is where the problems started thinking back. I've since filled it up with normal unleaded so maybe your on to something here.

Kind regards,
Adam.
 
aragorn said:
Yeh you really cant be running 95 octane fuel with the MAF swap, need to keep it on the good stuff.
Click to expand...

Just a little update. A tank of high octane fuel sorted this problem out and she's running spot on now.

Thanks for all the replies.
 
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