View Full Version : Renntech ECU upgrade

02-03-2012, 06:56 AM
Buddy of mine just got the renntech ecu upgrade put into his GT 535 ...HP increase to 370..said he think its faster and more nimble then the 550 because of the reduced weight and he is seeing very little difference in his gas mileage... Ill drive it this weekend to see... Of course this just days after my GT finally showed that it went into production...hmmm could i have saved a few thousand dollars and had better gas mileage?? And had no one know what was under the hood??

Ill report back on monday!

02-03-2012, 04:43 PM
Interesting. Will be watching for feedback.

Not sure if it is still the case, but the 550 GT were leasing out less expensive in Oct-Dec of 2011. Anyone know? ...Even though I went 535.


02-04-2012, 05:46 AM
i had read that initial post back in december as well.. but when i went to buy in last dec it was not the case.. perhaps on inventory where dealers were willing to go as low as possible on their stock.. i think now the dealers have all figured out how many or few gts they are selling and aren't really bringing many in...

it s so hard to even find gts to test drive... i was really lucky that one dealer within 75 miles actually has a 550gt drive with sport for me to actually drive....not one dealer had one with many of the pkgs i wanted.. good thing this forum is here to ask others questions.

i know now the 550 is leasing out a few hundred more per month...

not sure but if this renntech is really delivering 370 with so much less weight and 23-30% better mileage i might have gone that route...

now all i need to do is mod the stock 550 exhaust, i fall into the category of hating square tail pipes....hoping i can find twin rounds to replace the stock tips with out it causing much trouble...M pipes would look so good on the back of a 550..

02-04-2012, 06:01 AM
Unfortuantley it was the 2012 ordered ones that had the good deal. Dealer inventory was priced out (leased) higher on both cars. Go figure....

I test drove a 2011, then found the pricing and options, and ordered for delivery. I would really like the Dinan kit if/when avaialble since it rides on BMW's warranty and is serviced by my dealer (Thompson). We'll see if it makes it up to the 535GT.

Good luck with your GT! PS - I switched my tires out too, awesome upgrade vs the LS2's it came with. I have the LS2's stored, and will put them back on at lease turn in time :D


02-04-2012, 11:19 AM
If I interpreted the power/torque curves properly, it peaks power earlier than stock, but falls off faster at higher revs. Will be interesting to see how it feels out on the road along with any differences in fuel use.

02-04-2012, 08:27 PM
Ok drove the 535 M sport with the renntech today... HOLY S...
really fast....and nimble and better exhaust sounds...still tame but better..

Ended up needing to drive it over to pace bmw as they had a 550 gt to test drive (no M reg sport)

must say i liked the 535 renntech better... no stop watch but def pinned you to your seat as well as the 550...may have handled better..also hard to say...so i took a 550ix out after the the gt and i must say the 535 renntech had more in common in feel with the 550 sedan then then perhaps the 550 gt...

Must be the weight and its distro...but it did seem better in the curves of the Hutchinson river pkwy...


02-05-2012, 04:15 AM
Interesting - who sells/services Renntech in the NY/NJ/PA area?

Only thing having me wait to see if DINAN comems out with something is the local dealer sells/services/installs their products.

02-05-2012, 09:44 AM
The Renntech mod is very intrigueing. How do you get all that power and torque so early in the rpm range? BUT - I assume this mod will kill off my BMW warranty, True?

Also, I remember reading somewhere - BMW stating that they had tweaked the 535 GT and could not get much more power than stock. My faulty recollection is about 330 HP. Understanding that this is all a tradeoff of power/tourque vs. fuel vs. emissions vs. hardware stress - I wonder how severe the tradeoffs are?

Does not hurt that the cost is about half of a Dinan mod.

06-08-2012, 04:34 AM
Anyone have an update on their 535i F07 Renntech ECU experience?

Curious about power delivery, engine stress, and cost difference between the Renntech and Dinan. I do know about the 50k warranty with Dinan vs. nothing with Renntech.

06-08-2012, 05:32 AM
I talked to them a couple of weeks ago and they did not have a package for the 2012 F07 yet. Apparently BMW modified the software and they were still working on breaking through the firewalls.


02-11-2013, 09:59 AM
any news about renntech or dinan and cost associated with it

02-11-2013, 07:18 PM
I have the 550 and find that the 400 HP is plenty. But then again I drive like my Mom. Never going over the speed limit and driving it like its on egg shells. But on the other hand my wife drives it like she stole it. I must admit that when I do hit the gas it scares me. I guess I'm just getting old. :-)

02-12-2013, 01:40 PM
I hate to burst a bubble but it's not going to be close. 445hp in the 550 carrying 270extra pounds is going to walk hard the 335 pushing 370hp (if what they say is accurate and not greatly exaggerated).

In general though ECU tuning on the 335 motor is something I've got a good amount of experience with. You can easily get 40 real hp with no other supporting mods by tweaking fueling and boost. The same thing can be done on the 550 motor at the same price point. In either case it won't effect freeway gas mileage as there is no change to the engine at that point, but in both cases your performance driving will see significantly worse MPG. Although I've done it in the past, because when I'm on the track I don't care what my MPG looks like and it's usually in the low single digits anyway.

Reality is that these changes effectively will push problems with your motor outside warranty protection. Now small changes (stage0/stage1) will typically see 30-40hp/tq gains and are likely undetectable and safe. Anything beyond that is going to start costing you quite a bit in supporting mods in addition to the obvious detection on physical detection as well as the ECU tattle tale codes that BMW puts in for just this purpose (yes I'm familiar with these).

My Summary is I love mods, but you have to account for real total costs and do fair comparisons. Otherwise I'm happy to put my old 2.0L Subaru up against any stock BMW and given the price difference I could say it's superior, but clearly if I believed that I wouldn't be driving BMWs.

02-12-2013, 01:44 PM
Oh and if you're really interested in mods for the N55 engine, check out Terry's company: http://www.burgertuning.com/
I've run there stuff in the past, and he does fantastic work and really knows his way in and out of the N54/N55 engines better than most anyone and has been there since the beginning. I can't say much for Rentech personally, but with some quick research BMW is there second gig, and they go about tuning in a different fashion entirely that by default will have a higher cost basis. Something to compare is all......

Disclaimer: I'm not affiliated w/ Burger in any way.

02-14-2013, 05:48 PM
I tried tagging on tuning chip for GT 535 on burgertuning.com but it throws me off and does not allow a buy option. Texted Terry 2 weeks ago still no reply

02-14-2013, 06:47 PM
not sure what you mean by tagging on tuning chip? I've always had great responsiveness from Terry via phone or email in the past though..... Hopefully you'll get through soon.

02-17-2013, 04:40 PM
Tagging...sorry, I meant when I go to buy option it does not have option to buy to 535GT