I have an 04 MCS with a ton of mods - in this case the relevant ones are CAI, UUC exhaust, plugs, wires, coilpack, 15% pulley, and 63mm throttle body.

The minute I put on the throttle body, I noticed a flat spot somewhere between 2800 -3300 rpms, pretty much consistent in all gears, but definitely more noticeable in 1st, 2nd, and 3rd.

I don't have any ECU mods and was wondering if it's really the version of software causing the problem or if it's the throttle body.

Well, went to the dealer today and was told I had v43 of the software, with v44 being the latest out there.

Somehow (don't ask me how) I mananged to get the JCW ECU update and now the flat spot is all but gone. I can kinda-sorta sense it in first gear only and the car pulls much nicer in general.

Has anyone else done the JCW ECU mod on a non-JCW car? If so, what are you thoughts?

MTH supposedly has a flat-spot-fix version of their software....and based on everything else I've read, it seems to be a software only problem....

Hm........

 

I have the MTH tuner, and while the flat spot is reduced, it's not gone. I also don't know if the TB really adds anything at all, at least not until you really improve the flow through the engine. When I tested stock, 60mm and 62 mm with my G-Tech, I didn't measure any power difference..... But I'm still running a stock head, and while I have a header, I don't have a higher flow cat or a real free flow exhaust on yet....

Matt

 

For those who have 15% + 2% and CAI with a header/cat and cat back (ultrik/milltek) would it be of reasonable benefit to add larger injectors (i.e. 400) and larger TB (i.e. 62)if the head work only consisted of porting the
exhaust and a schrick cam without larger valves and springs? Flat spots
seem to occur under every scenario unless extensive ecu work is performed.
Please excuse me if I've taken this off topic.
mike

 

Larger injectors will do nothing until the stock ones are inadequate (leaning out). At what point does this occur? Dunno. On another thread someone speculated 250 HP but that is just that - speculation. Only way to know is to monitor F/A under load (not necessarily dyno). As to the TB, it seems TB size would have much more effect on a normally aspirated engine. At any point do you see a pressure drop across the stock TB?

 

I have a 15 psi boost gauge (taps out all the time) and after swapping out to a bigger TB I have not noticed any difference in boost.

The throttle response is much improved (compared to the car bone stock when I had that annoying stumble/lag when moving from a standstill) and in general the car pulls a bit better (butt dyno talking?).

After having the ECU flashed today, perhaps I am just experiencing the re-adaptation of the ECU.....so maybe I should drive it like I stole it for a while.

A/F gauge is a good idea. I will have to do my research but I maybe just put it in my driver side vent next to the speedo (I've got a voltmeter in the passenger side vent right now).

Dr. Obnxs, wasn't it you who posted something about A/F leaning out like crazy after a bored out TB install to 18:1 where stock was something like 12:1? I can't remember the details.

 

When is it necessary? With catback, headers, 15%, cold plugs, CAI do you need it? or is it an overkill? Info needed, thanx, sorry for the hi-jack

 

You see my mods 380s were not enough to keep me out of lean..... I have a head/cam, header, TB.....intake manifold/runners Alta IC .... Alta CAI and the 400s were necesary

 

Spider, how about the combo i wote above?

 

Anybody have any thoughts on the JCW ECU mapping? I don't even know what the mapping looks like. Does anybody have it downloaded so that one can view it?

How does the JCW ECU mapping compare to the MTH/UNICHIP/GIAC mapping? If the stock ECU mapping runs rich (9:1), then what does the JCW mapping aim for? 12:1?

All I know now is that the flat spot is almost completely gone and I get to enjoy the car that much more......

 

The flat spot is lean operation. I have a wide band (if you add one of the guages that runs off your narrow band, it will tell you lean vs rich but not how lean or how rich). Some of the numbers were friggin' scary!

Personally, I didn't see any HP advantage with a larger TB, but I haven't really opened up the air flow path as much as is possible (head and exhaust to go), so it may add value there, but for close to stock cars, I'd spend the money on a hood scoop, as that will lower charge temp and make real improments...

Matt

Also, I don't know about the improved tipin response. The drive by wire is predictive, and if you start to hammer the gas, it open the TB up faster than you can. I've seen this in data logging. If there is any tip in improvement, it's at the price of risk of the flat spot.

 

Nice

 

About to install the VGS. Can't believe I've missed out on this for so long. Perhaps that will completely remove the flat-spot.

Has anyone got any experience with the $50 Autometer 4375 narrowband air/fuel gauge? I just want to know if I'm running rich or lean........will the wideband react more quickly or will it just measure the leanness/richness more accurately?

 

A narrow band just shows if your rich or lean, a wide band breaks it down to numbers. This way you can see how rich or how lean you are. When modifing this is good to know so you dont cook your pistions.

 

Lord of the flies can you please PLEASE take photos of the VGS install??

i think it would be a great addition to andy's diagrams etc and give the others out there a better idea of how to wire up the hoses etc.

 

i have a simular mod list to what you describe.. i have stock injectors and have no issues with running lean.. take a look at my dyno graph.. while the A/F mixtures could be little flatter, it shows no problems with running lean.. infact it shows richness..

https://www.northamericanmotoring.co...t=50746&page=6

 

Sure.

Having already done the boost gauge this will make my life even easier.

Hm. I wonder why at slight throttle the car runs lean then - you'd think that at WOT you'd have a lot more air to deal with....but maybe the ECU is more binary than not, i.e. spray lots of fuel or spray too little. Funny this didn't happen before I did the TB.

This morning (a bit chilly) I definitely felt the flat spot during the initial few minutes of driving...After warming up I think it was reduced a bit. Hm....

 

but it is indeed a mystery as to why the ECU hackers can't seem to make this go away completely.... But it isn't a WOT effect at all, only very slight throttle, and certain RPMs. If you have it, you know you can make it go away by stomping the throttle. Wouldn't really be an issue on the track, but sure is cruising on the freeway.

Matt

 

From my reading, the flat spot is created from the throttle body. That is why M7 has the smaller bore TB offered.

 

But the flat spot isn't gone, and I don't think it's right to say that the TB causes it. Remember, we have a drive by wire system, and it's the interaction between the TB and the TB control that brings this up. Also, for cars with much less mods and tune optimization, it doesn't seem to be a problem either...

Matt

 

Here you go Skuzy! With pics and some notes......

https://www.northamericanmotoring.co...513#post792513