The reality is that there are only modest gains to be realized in just retuning a stock system. The real gains are made tuning to specific mechanical changes eg. camshafts,

I'd be interested to know what these tuners are actually changing on stock engines. I suspect they are forcing the system into open loop ( like that which is available at Wide Open Throttle) and taking advantage of the A/F tables for that condition-open loop ( usually leaner). The problem with this is that it ignores any O2 Sensor control , which could have implications regarding it's ability to pass emissions tests and possibly could cause roasting of your cats.

 

I would like to know what parameters are being adjusted and to what, generally speaking. I emailed one of the ECU tuners about this and no response. Intake mod and info (check), pulley mod and info (check), tune mod and info (secret ).

 

OUCH!!

 

OUCH!!!!!!!!!!!!!! LOL

 

In Steve's defense (not that he needs it), there weren't that many options or places to get mods during the time he got his.

 

There were a few other cheaper ECU tunes w/no pulley's avaliable, but buying cheaper - sometimes you get what you pay for and they were questionable. It was a brand new car and I wanted the best for it, my only chioces were RENNtech, Kleeman or Evosport. But once I found out those RENNtech badges added an 10HP, I went with RENNtech and got two sets of badges for an extra 20HP . Although there are cheaper ECU/pulley kits avaliable, I have no regrets going with RENNtech. Having an ECU/Pulley kit from a prestigious company like RENNtech is worth something .

 

Im running 11.8-12.5 A/F in 1st 2nd and 3rd gear, in 4th its 12.4-12.5 all the way up to about 5500rpms then it shoots straight up to 16.8-17.8!

My tuner says hed like to see 11.8-12.0 on pump gas and that my consistent 12.4-12.5 is too lean for safety. But you guys seem to think thats fine. Has anyone installed an A/F gauge on a stock car and what was the A/F? He wants to know what Mercedes considers safe from the factory.

As far as jumping up to 16-17 its lack of fuel, either injectors or fuel pump....after everyone says they are plenty suffecient.....i think not.

Im currently running colder ngk "7" plugs stock gap of .039 but now im considering dropping that to .025 to se if it makes any difference in the A/F readings.

What you guys think? The last thing i want to do is tune it leaner if its already too lean.

 

I did see a post here a few weeks ago that stated that most tunes use the SLK 32 AMG map, and that can cause a problem with a Crossfire since the SLK injectors are higher capacity. I couldn't find that thread, but I did find this post by HDDP:

Thanks, I know those guys... Good group of people... I like using Doug at http://www.lindertech.com I have had great experiences with him... And you can't beat his resume'... He already has my injectors and is going to flow test them on Monday. That's what sparked his call... He opened the box and said these are not the standard injectors from the 112 engine, they are lower flow...

The point behind my previous post was that DCX has installed lower flow injectors into the Crossfire than the normal MB 112 engine... This is probably to increase fuel mileage numbers... Which obviously hurts HP... There is an 11 lb difference between our injectors and the injectors that were spec'd for the 112 engine...

 

My car was running 10.6 AFR at WOT to redline in 3rd gear with SL55 intake as my only mod.

 

It's understandable in his case as you mentioned there wasn't many places to go. That's how it goes though with the whole supply vs. demand deal of having a niche car. I have always been a fan of Renntech power gains but their prices are outrageous.............just go to their website and look at the prices for mods on the V8 and V12 AMG cars. I am also a strong believer in the "you get what you paid for" saying but at Renntech "you get bent over for what you pay for".

 

Well, coming from the turbo world anything leaner than 11.8 is offically "too lean" in my opinion. So I can see where your tuner is coming from.

As far as what is acceptable in a hand built AMG motor, I would ASSUME you could go a little leaner.

I hear 11.8: I think safe

I hear 12+: I think not safe

 

Beware of "Budget" tuners.

Thos who claim to be able to tune Bosch Me2.8 in 15 mintes on the dyno have no clue about that engine management system.

 

I too was in the same boat when I was looking for perf. upgrades. Only reason I went with SI instead of Renntech is that SI was local to me so if something got screwed up I can easily go to their shop as opposed to getting stuff resolved over the phone.

Like Steve said it was pretty much just SI, Evosport, and Renntech at the time that had an ecu+pulley package.

Now there's plenty of choices and cheaper choices at that and more importantly a lot more people now have had first hand experience with them so peeps can now factor that when making a decision as opposed to the manufacturer just posting claims with no dyno or other proof.

 

240M3SRT...any progress on your tune? Are you going to run it this Friday with it leaning out this much?

 

I ran a rock steady 12.5 AFR from 3,500 RPM all the way up to 6,200 RPM. I have 6K+ semi-hard miles on my SRT since with no signs of peppering on the plugs. Actually the plugs look really good!!

I'll have an opportunity to Re-Dyno my SRT once I've completed my IAT mods to see if anything has changed. I will probably use the same dyno that SRT6 Dan used and save me a trip to LA.

Give Erick @ LET a call - I know he was running way lean with 185mm Pulley on his MB and I ran way rich with the 185mm. I provided him the Chrysler part # and the Bosch part # for the injectors on my SRT.

I Agree - It took SI about 5 hrs. on the dyno to really dial mine in. It was a great experience to actually watch the process and view the results. About a 30HP Gain. I wonder how the "bench tuners" do it without any parameters to measure?

 

In short, probably so. Im going to run it hard a few more times on the road to check for a/f consistensy.

 

What gap are you running? I had the colder #7 ngk plugs at a stock .039 with 12.5 afr's. I went back and lowerd them all to .025 which is a huge decrease(what MD SRT6 is running 11.2's in the 1/4 on with nitrous and 181 pully and nitrous). I ran the car again and the freaking a/f went up to 13-13.4, wtf!

Brian, do you see your a/f being greatly affected by outside temperature? As in .5-1.0 higher a/f for every 10 degrees drop in temperature.

 

You're probably getting incomplete combustion due to the smaller gap/colder plug, or your car is going into enrichment from IAT/H2O temps.

Datalogging will tell which it is.

 

I am running the NGK BKR7EIX-11 Iridium series plug gapped at .039. (per the Chrysler service manual)

The NGK website said that for cars running higher compression - forced induction engines running denser A/F ratio will require smaller gap - but I am not running a denser A/F ratio, and the SRT coils provide plenty of power to spark at .039 gap plus we have two plugs per cylinder. I think .039 gap is fine and works great for me. .025 seems a bit extreme. I would pull a plug to see if you are bridging between the electrodes.

 

If the monitoring device ie.. wideband or tailpipe probe are behind the cats(all 4 ) it throws the reading off by .50 roughly because the cats burn up some unburnt fuel. 11.0 would really be 11.5 on the rich side and 13.0 would be 12.5 on the lean side. Gotta keep this in mind. And if you lift the pedal at all then reengage the engine will dump fuel and you will be temp. lean but then it will richen back up as soon as it sees you reengage. These are some complicated *** cars. But once you understand how they work it's all manageable. Temporary leanness on these cars is ok as long is it's not more than 1-3 sec's, I ran 13.1-1 for over 15 minutes on the dyno and not even a nip at the electrodes. Hope this helps some! This is all considering no meth and no nitrous because with either of these you need a much richer environment like 11.0-1. By the way in your case I would gap the plugs at .030 -.035. The wider the gap the leaner the engine, the closer the gap the richer the engine to the point of misfire. The only reason my gap is so close is the nitrous was blowing out my spark. You should not have to go this close.