M177 Engine - Stage 1 Tune on 91 - Worth it?
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Joined: Oct 2005
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From: Vegas
'21 GLC63, '19 M5
M177 Engine - Stage 1 Tune on 91 - Worth it?
I'm considering a RENNtech ECU+ Upgrade setup for 91 octane.
When reviewing the dyno graphs for tuned M177 engines, it looks like the power and torque falls on its face after around 5.5K rpms. In stock form, I can already tell that the engine is running out of breath at the top end. Will this be even more evident with a tune? If so, then is the tune really worth it if it makes this issue even more apparent? Looking at the RENNtech dyno graph attached, it seems to add insignificant power up on top, with most power gains had in the middle of the power band. I don't know if that will make the car feel like a rollercoaster with power only appearing in the midrange of every gear. I'm not interested in doing any additional mods to help the engine breath better. So it's a Stage 1 on 91 or nothing at all for me. Lastly, do I need a CPC tune to feel the stage 1 ECU tune do its job?
I appreciate those with Stage 1 tune to chime in, especially those running 91. I'm one of the lucky ones to get ***** gas here on the West coast.
TIA!
When reviewing the dyno graphs for tuned M177 engines, it looks like the power and torque falls on its face after around 5.5K rpms. In stock form, I can already tell that the engine is running out of breath at the top end. Will this be even more evident with a tune? If so, then is the tune really worth it if it makes this issue even more apparent? Looking at the RENNtech dyno graph attached, it seems to add insignificant power up on top, with most power gains had in the middle of the power band. I don't know if that will make the car feel like a rollercoaster with power only appearing in the midrange of every gear. I'm not interested in doing any additional mods to help the engine breath better. So it's a Stage 1 on 91 or nothing at all for me. Lastly, do I need a CPC tune to feel the stage 1 ECU tune do its job?
I appreciate those with Stage 1 tune to chime in, especially those running 91. I'm one of the lucky ones to get ***** gas here on the West coast.
TIA!
Last edited by DirtyVegasMB; Sep 26, 2023 at 10:55 AM.
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glc63
There is a quite a noticeable difference between a tuned GLC and untuned. Part of what you're describing with the power falling off in the higher rpm range is due to the small turbos and the stock airbox being restrictive. Any particular reason you don't want to do an intake? I saw a difference of 3 mph in the 1/8 mile compared to my baseline on the dragy after install. Baseline was a 91 tune vs tuned with intake. That's a pretty significant gain. To your original question though, I would have the CPC tuned if you tune the ECU. Have you thought about tuner other than ReNNTech like eurocharged, labworx, AMR?
Thread Starter
Super Member
Joined: Oct 2005
Posts: 689
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From: Vegas
'21 GLC63, '19 M5
There is a quite a noticeable difference between a tuned GLC and untuned. Part of what you're describing with the power falling off in the higher rpm range is due to the small turbos and the stock airbox being restrictive. Any particular reason you don't want to do an intake? I saw a difference of 3 mph in the 1/8 mile compared to my baseline on the dragy after install. Baseline was a 91 tune vs tuned with intake. That's a pretty significant gain. To your original question though, I would have the CPC tuned if you tune the ECU. Have you thought about tuner other than ReNNTech like eurocharged, labworx, AMR?
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glc63
That would be nice if ReNNTech has the ability to reset the flash counter but wow they’re expensive. My warranty runs out in December anyway.
Some of the tuners have sales if you keep your eye out or will give you a good deal if you talk to them. I’ve seen under 3k for both the cpc and ecu tune. My tune uses the wife’s laptop to flash back and forth between different maps and the stock file. You will need a new cpc to flash, tuners will either send you one that they flashed or read your old one through the obd port then have you install the new one and flash it. Intakes are probably the easiest thing to revert to stock if you need to take it in. I think it took about 10 minutes to install with a screwdriver and pliers for the different clamps. Everything else just pops off.
Some of the tuners have sales if you keep your eye out or will give you a good deal if you talk to them. I’ve seen under 3k for both the cpc and ecu tune. My tune uses the wife’s laptop to flash back and forth between different maps and the stock file. You will need a new cpc to flash, tuners will either send you one that they flashed or read your old one through the obd port then have you install the new one and flash it. Intakes are probably the easiest thing to revert to stock if you need to take it in. I think it took about 10 minutes to install with a screwdriver and pliers for the different clamps. Everything else just pops off.
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GLC 63
I was looking at RENNtech because of the handheld module that gave you an opportunity to flash back to stock tune, and the fact that it supposedly also erased traces of a flash (resets the flash counter). I don't want any traces of a tune when I bring in my car for dealer service. I still have over 3 years worth of warranty and I want to keep it. Same for the intakes, it would just create suspicion that my car is not stock. As for CPC, that along with ECU+ from RENNtech just did not make financial sense at $5.5K. Is CPC programmed from OBDII, or is it a more invloved than that?
