Hi all, I've been lucky enough to get to test an M7 60mm throttle body. I got the larger one, and it appears the ECU upgrade for the CA emissions recall isn't too hapy with the big one, so the guys at M7 were nice enough to make me a 60mm to try.
For those that have not been reading up on the larger TBs, the biggest ones seem to have a severe flat spot from a bit less than 3000 RPM to a bit less than 4000 RPM at light throttle. This is made worse with very high flow exhausts, so bad in fact that I cooked my Magnaflow cat by having very high exhaust temps.... During the flat spot, the car runs hellishly lean (I have a wide band O2 sensor and an Exhaust Gas Temp monitor to measure with). The A/F ratios would go to almost 18:1 and EGTs topped 1050 C. since my commute was right around these RPMs, I cooked the crap out of the cat.....
Anyway, here's what I've found.....

I'm up about 8 peak HP with the 60mm TB (G-Tech numbers). This is probably +/- 2 HP on the delta, it's been a while since my last baseline. My peak HP is at 6400 RPM as well, which is interesting in itself...
The flat spot isn't completely gone, but it's not an issue with drivability, and even though the mixture leans out a bit, it's not nearly as bad as the 63mm, and EGTs stay less than 950 C at the worst of times, and in the upper 800s when I'm driving hard most of the time.

All in all, I'd call it a winner!


FYI, I'm running HAI, JCW injectors, 60mm TB, OBX header, Stock cat, One-Ball exhaust, and MTH standard map.

Matt

 

Great report. Where did you get your wideband sensor and your A/F meter?

 

Look here for info....

 

thanks!

 

Oh, a quick question, in regards to exhaust temperatures, what is driving them to be high? Is it the A/F ratio being too lean? If so, does richening it up solve the high exhaust temps? I ask this because I too do much of my driving in the same situations as you. In regards to pinging / pre-detonation...Are they the same term for the same thing where the ping is the audible portion of a pre-detonation? Can running too lean cause pre-detonation, or is it a function of timing?

 

LEan can lead to detonation, and timing can lead to a bunch of gas buring in the header. I honestly don't know what's up here. I've been logging data, but I haven't seen anything obvious.

Matt

 

Matt, thanks for sharing your homework with us! As you know, I have a fairly free-flowing exhaust, so I find this info very interesting. I think I'll be getting a 60 from Peter fairly soon; with your results helping me in my decision-making.

 

but Tony, it won't really save much weight!

Matt

ps, if you do get one, drive it for a bit before you send in your stock one, just in case there are issues. I'm still digging into the data logs to see if I can see anything, but so far, no luck... -M-

 

Oh, I went down the TB road about 2 years ago, so the stocker will indeed stay with me until I'm convinced I finally have a winner. Thanks again Matt.

 

Dr Obnxs, Have you run those tests without the MTH standard map in place?
I thought thats what the MTH did was Mod the fuel and timing maps on the lean side for more power. From my motorcyle and VW air cooled Mod experiences, when you change the intake filter to make it free flowing / add a header your always into the carb's jetting them up for more fuel. Any Mods to either of the above will tell on you real quick. I know we have a ECU making those decisions but the MTH is telling those injectors to do something else.

 

Matt,

Noticed you are running with the MTH standard file upgrade. Have you thought about trying out the Tuner upgrade to see if that would take care of the remaining flat spot?

 

Just out of curiousity, how long (miles) had you been running with the larger TB before you noticed you had cooked your Magnaflow?

 

I've got too many mods to run stock mapping, so I didn't. But if you read the threads on the flat spot with larger TBs. Those that went from stock to MTH haven't had the flat spot behavior change, so I'm thinking that what they're programming isn't where the problem is. I've thought about the tuner map, but before it existed, MTH was willing to tune your map based on A/F numbers, now it seems that's not the case for the base tune, so I may take the plunge before the conversion is complete. Everything you said (norm03) about carbs is correct, but they can never run in closed loop mode. So while the ideas are good, I don't think they transfer to the newer fuel injection. If the closed loop programming is good, it won't matter what you bolt on... It's the WOT maps that need the leaning and spark correction to really get the most power.

I drove for about 2-3 weeks with the 62/3 mm and the race exhaust. My commute is ~60 miles round trip, so that would be somewhere between 500-1000 miles. I knew it was done when the exhaust noise GOT EVEN LOUDER! The cat material isn't broken at the front, but it shure is discolored. My cat it welded at the back (No two bolt flange) so it will take a sawzall to see what the rest of the cat material looks like. The 1050 c was about 6 inches in front of the cat, and the cat reaction creates more heat, so I expect the damamge to be at the back of the cat, not the front (but I haven't looked, so that's just a guess).

Hope this helps...

Matt

 

out of curiousity were is your egt probe located?


EGT probe location is crucial! I had an egt gauge on my turboed civc si and when i finnished the car i drove it to the dyno with some "estimated tunning" the egts were leading me to believe that the a/f was rich... then i got to the dyno and got an a/f from the dyno... boy what a difference! my car was running so incrediably lean (which should have shown up on the egt gauge as really hot) and i was very fortunate that i had 107 octane in the car otherwise i probably would have had alot of nice "unique" christmas ornimants. Because of this i no longer trust egt gauges... the only thing to trust is the wideband! The wideband tells you just about everything you need to know!

 

in the PLX-500 installation thread. It's about 3" from the end of the header. And I have a wideband as well, so I get both sets of data. With the EGT so far from the exhaust port, the gasses were hotter up by the head. I pretty much discolored all the SS in the exhaust system. It's now golden, instead of shiney silver....

Matt

 

seems to me running too lean midrange is a sign there is more power to be had by adding gas to improve A/F, not cutting back airflow. a large part of engine tuning is to get that airflow up there, you just have to bring the fuel along with it.

 

Good info guys, I had a Webb BBTB and it crapped so it was replaced by an M7 probably the 63MM I am running lotsa mods including the Unichip on Map 10, I threw a lean code after 100 miles of freeway speed control driving, am using the B or high octane map as it always ran oK with no codes, anyone doing the same, and will switching to A map eliminate the problem? I agree, maybe the map needs to be reprogramed to get more fuel to go with more air?

Thanks

 

Hey Matt, my MCS has that flat spot you described in the 3000-4000rpm range, noticed it as soon as I left the dealers after that ECU down grade.
Are you suspecting that has anything to do with yours at all?

 

But I haven't seen that the MTH tunes really deal with it well, and it's at part throttle only, so the WOT maps seem to be fine, when it's just slamming the TB open.

I'll be hunting through some data to see if I can pin-point it, but I think a real easy fix would be to use the TB control code from v 36 or so, but I haven't seen anyone do this yet.

Matt

 

I agree.

My question is if it's lean at part throttle (closed loop) why isn't the ECU correcting for it? If the ECU were anywhere near it's max correction you'd have CEL for long term fuel trims..... :smile:

 

It doesn't last all that long, unless you drive at that point all the time. I did throw some codes when it was at it's worst (63mm and free flow exhaust, lean condition, P0117, I think, but I'm not sure) But I'd clear it and go about my business.

Matt