Here is where it gets a little more fun. I purchased the car a few months ago. I went and looked at the car and drove it. The car was about to expire on its factory warranty. (buying from a wholesaler who is also a friend) The car was then sent to mercedes to be picked apart while it was free. Mercedes replaced the i/c pump and the car felt faster afterwards. I never thought there was any kind of problem (power wise) until I saw the track times. I checked the air box pieces and those are in place. I will check with marcus frost and see what happened in his case. Someone asked about my 60 ft's. They were horrible due to poor traction. I had traction control off (not in dyno mode). It feels like the car is losing its power up top. The low end is great.

 

Interesting.

Well, running out of power on the top end, is usually due to the car pulling timing because of excessive IATs. What causes high IATs, you ask? Most of the time, it's a faulty I/C pump, so we're back to that. The fact that the car feels strong down low, tells me that you don't have a boost leak, since peak boost/Tq comes on early in these cars. My gut still says bad I/C pump.

One post mentioned too much hp/tq from the tune. Yes, that can happen in cars that don't have a TCU tune (like yours), which effectively raises the torque limiters, so the car doesn't neuter itself with a high HP/TQ ECU tune, so I don't think it's that.

If the dealer did the warranty work on the I/C pump, it will be warrantied for 1 year, even if you car is out of warranty. I'd take it back there and have them look at that again.

If that fails, then I'd take it to a dyno, so you can see exactly what your IATs and timing are doing. Do you have a data logger? Might be time to invest in a basic one, like the AutoEnginuity, so you can see that stuff without going to a dyno.

Have you talked to Jerry about this yet? If all else fails, I'd have him flash you back to stock, and re-run your tests.

 

or the OP may just like to trade it in on a GTR and be done with it and have a mid to high 11's right outta the box heck Camdon is at mid 10's w/ a 997tt with just tune and exhaust

 

I appreciate the suggestion but Im not looking for a $70k nissan. I like my sl65 as my beater. I have my z06 for other things.

For the previous post I think that i wll replace the i/c pump. I was going to talk to mercedes about the warranty but I may as well get the johnson pump at this time. All things seem to be pointing to that. Jerry wants to get it on the dyno and see what it is doing as do i. I just wanted to get input prior to that so that I don't pay for dyno time to find out I should have looked at something else first and then have to re-dyno it.

 

Get a Fuel Pressure reading...I'm running into a similar issue and will be going through diagnosing it next week.

Fuel Pressure should be 60-61psi. Low FP would lead to lean A/F...pulling timing...hence less HP.

 

Should I just check FP at idle? Is there a schrader valve somewhere for the attachment? (i haven't looked)

 

Yeah, feedback I have is FP is static...so getting a reading at idle should be fine. I haven't looked personally either yet - but Marcin's told me it can be tapped at the passenger side fuel rail.

My local shop (broadway performance) also things there's a way to read it via another scan tool...however...not by way of "normal" OBD logging and scanning - maybe via STAR diag?

 

mb has a fpr sensor? and when you say static does that mean it doesn't increase pressure when you go into boost?

 

On v12tt cars between 2003 and 2006 the fuel pressure is static. Meaning it does not change with boost. It has a pressure sensor and a pwm controller with a preset and it runs same pressure whather its idle or wot. There is no way to get a pressure reading with a scan tool on the 03-06 cars. Star diag. will not get a reading either. 2007+ cars have been changed. On the newer cars the fuel pressure is boost referanced and also runs diferent pressures for cold start and hot start etc. The newer cars have CAN comunication between the ECU and PWM controller for the fuel pump so you can get a reading through a good scanner or the MB star diag tool.

 

Marcin....what would you guess his problem is? Sounds like I/C pump to me, but OP states he just got it changed by the dealer.

 

I will tell you exactly what is happening, not sure why nobody mentioned it yet. For starters I'm going to go over a few things that need to be understood, I appologize for boring you with details.

When you are drag racing and lay down a poor 60ft time the trap speed should actually be higher than a pass with a good 60ft time, wheel spin out of the box hurts your ET but actually results in higher trap speeds, I know that it probably does not make sense but trust me on this one. My quickest ET trap speed is over 4mph slower than my highest ever recorded trap speed which was over 2/10ths slower than my record ET...you still following me?

What you are explaining with your ET/TRAPS goes completely against the what I've explained above, that tells me one thing, when you are experiencing your wheelspin you are letting off the throttle way too much, you are losing your momentum and drive, the motor looses its revs and you're no longer operating in your peak rpm and hp range, I imagine this gets exagerated in a turbo vehicle because of a reduction in boost when you came out of the throttle for that split second.

Try to give it less gas out of the gate and build up rather than letting it rip only to have to back out of it, a fraction of a second off throttle and your pass is shot. The fact that you are putting down 2.2 60s tells me that wheelspin is beyond excesive and you're probably already out of the throttle before you cover your 60 ft or your smoking them so bad that your off throttle well before the 1000ft marker. If you posted a couple slips we could see exactly where its happening by calculating 60ft, 1000ft and 1/8th compared to ET.

Don't take this the wrong way, its not meant to be an insult, but it sounds like these are brand new mods, significant changes in hp, torque and power delivery are going to require a different launch and driving method. I have no idea of your level of experience with your car or your level of experience with drag racing. What I do know is that I drag race my car a lot and I run with and without nitrous regularly and I have a definetively different driving style/launch technique for each, if I launch the car on NOS like I do NA it usually results in an ET slower than my non NOS passes, if I launch NA as if I was making a NOS passes a Chrysler minivan could probably beat me. Before you start tweaking stuff and ripping stuff apart and trying to diagnose a problem that might not even exist get back to the track and be sure you have ruled out pilot error, we are all guilty of our ego and ignorance from time to time. You are running a proven package with your mods, chances are its not the car.

Good luck

 

Jim:

I don't disagree with your rationale above, I just don't think it is the complete answer to this problem.

My completely stock CL65 (no drag radials) never trapped below 118mph in 85-90 degree humid weather when I ran it. The 1/8 mile trap speeds on those runs were always 91-92mph. The OP's best 1/4 mile trap speed is 117mph with a 94mph 1/8 mile trap. If it was purely a problem of him getting out of the throttle, it would result in a really low 1/8 mile time, but he would at least pick up 26-30mph on the back end. That doesn't seem to answer the really low 23mph pick up on the back end of his best run. The Op's SL65 just doesn't seem to be running right throughout the run and not just on the front end.

Tom

 

Tom, I hear what you are saying but my rational is this. I've driven a couple of these 65's both on the street and at the strip. IMO they are difficult cars to drive quickly and I know how to drive and launch a car. I am by no means an expert in a 65, they do take some getting used to, they are far more difficult to launch than a NA or SC car due to the power, torque and more importantly they way they deliver that huge power. Obviously you know these 65's 1000x's better than me, but from my breif experiences with them I've found launching them is a b!tch, the brake stall has to be perfect, you have to get the boost up so you don't fall flat, but too high and you're up in smoke. I do not know the OP's driving ability or level of drag racing experience. Has he been to the strip once or 100 times? If he is experienced what is his level of experience in a turbo car, what's his level of experience in his 65? I am in no way trying to insult the OP by questioning his ability, just trying to help diagnose the problem. If my theory is off it could be the exact opposite of what I stated, he might not be brake stalling it enough, too low of revs and falling flat out of the box, the only reason I don't think that is the case is that as you mentioned he's not picking up the MPH on the back end. I really think he's getting out of the throttle somewhere down the track and loosing his drive, momentum and boost.

I also mentioned the fact that these are new mods for the OP, we all know that new mods, increased power and torque delivery need to be learned and adjusted for. People think drag racing is easy, especially in these automatic 6 and 7 speeds but that's not the case, we have no clutch which in some ways is easier but it also makes us have to rely on a perfect technique and brake stall every time, finding that can take time and if he had it figured out when his car was stock he has to throw that technique out the window and start over because I gaurantee the optimum launch tequnique a stock SL65 is not the same as it is on a heavily modded SL making 100 or more HP than the stocker.

I might be 100% wrong with my theory, all I am saying to the OP is that before he tears his car apart and sends it to this shop and that shop to have things checked and rechecked he should make sure it's not pilot error. Pilot error is sometimes the hardest thing to diagnose but one of the easiest and least expensive things to fix. I'm not sure where he lives but if he is a less experienced drag racer maybe he can hook up in person with someone that is very experienced with a 65, maybe even let the more experience guy make a pass or too. Tom, I know for a fact that if you or another experienced 65 owner made a pass in his car you would know before the end of your first pass if it were a mechanical issue, right?

BTW, when did you pick up a GT-R? SWEET!!!

 

I am sure I would feel it. I would be interested to see if the OP could datalog the run on a vbox to see precisely how much time is being lost when the TCU torque limiters cut the power on the shifts. I was able to see that on my vbox when my CTS-V's TCM was hitting torque limiters on my shifts (no acceleration for over 1/2 second at 92mph which is an eternity at the track).

Thanks, I picked it up the GT-R about a month ago. I threw on a resonated (catless) mid-pipe, HKS air filters and Cobb A/P Stage 2 tune. It is a fun car especially now with those mods (which really wake it up).

Tom

 

OP has TCU tune, which raises/removes the torque limiters

 

Not sure but wastegate actuators, bov's (recirculating?), piping...if there is a problem with any of these , it can cause a dramatic drop in boost pressure as speeds climb and boost builds up. That's what it sounds like to me since your 1/8th mile trap speed is fine, otherwise I'd say maybe try dyno mode to rule out any kind of electronics interference. Whatever the case may be, good luck!

 

There has been a lot of great input and I even considered the thought about letting off due to traction and getting back on but I know that was the case in my lower traps but not them all. I borrowed my friends snap on scanner. In 49 deg weather I was seeing 97-108 iat's while cruising and saw a peak of low 120' s while on it. Is this normal? I saw a peak of 20lbs of boost. My timing was at idle -7 deg and on it saw up to -24. I'm assuming the neg mark doesn't mean its pulling timing but that is actually what it is advancing. I hope that I'm correct in that thinking. Do these numbers sound right?

 

It appears you have gotten a lot of good advice here.

I'm posting because I recently upgraded my EC tune in my 600. Not sure how recent your tune is, and it sounds like you are talking with Jerry, but I have Jerry's recent ECU tune (November) and also his new TCU tune. While I went through a few ECU versions to get the combo dialed in, my car is notably faster than what they were doing with the ECU last Summer. I have not been to a track yet to validate with numbers, but I am pulling like a freight train in 2nd and 3rd with colder weather.

If I were you, I'd put the car on a dyno asap to see what is going on.

 

that's what I intend on doing. It's tough trying to coordinate with everyone to get that done. It seems like January is the soonest. I want to make sure I've done my part to make sure ive covered some other possible reasons.

 

Stay tuned brotha...My ride will be in the shop on Monday and will be there all week to have a number of things gone through...including getting on the dyno. Dyno has a baseline from another tuned S65...so we know what we should see on this brand of dyno.

Re: trap speed and such...my best run was picking up just under 25mph on the big end with a 1.9x 60' en route to an 11.82 @ 118.8 - street tires.

Will keep you posted on what we find...hope we can both get it straight. Marcin if you're reading this...stay by the phone this week

Jay

 

Right on. Good luck. I'm looking forward to the results!

 

No codes or check engine light.

 

I don't know that the 23mph pick up indicates something is wrong. Mine had roughly the same gain. I went 97.1mph in the 1/8 mile going on to 119.6 in the 1/4 and mine's stock except for a better IC pump.
https://mbworld.org/forums/sl55-amg-...eline-run.html

 

Your 1/8 mile trap seems to be exceptionally high for a stock 65 (highest on dragtimes for any S/CL/SL65). But the OP has a tuned SL65, he should be picking up 25+mph on the back end, especially in the cooler weather. This would be especially true if he did something before the 1/8 mile to slow down his 1/8th mile trap (like the theory he let out of the gas). It would then show a bigger pick up in the back half (proportionately speaking). I was using the back half trap speed not as a hard rule, but merely to point out that whatever is wrong with his 65 isn't just because of something happening in the first half of the track, but happening throughout the run.

Also have been some tuned 65's that have run less than 25mph on the back half, but those cars had exceptionally high 1/8 mile traps (102+mph) and maybe were maxing out the intercooler's efficiency and getting heat soaked by the end of the run.

Tom

 

For a comparison of my tuned SL600, on my 11.40@120 run (Best ET, but not best MPH), I trapped 96.30 in the 1/8th, and 120.63 in the 1/4. For that run, my car had a base Eurocharged ECU tune.

My mph difference was 24.33, and I had a 1.70 60' on 20" boat anchors.