NITROUS OXIDE ( nos / n2o ) advice forum

Hi All,

Have been performing a couple data log runs at last on the Mini's auto transmissions.

I want to keep increasing the nitrous through the rear engine\transmission (currently at 50hp fixed hit) but don't really have a good idea how to determine if the limit of the auto transmission is being reached (until the obvious complete failure ) and thought there may be a few knowledgeable auto transmission people on the forum you could give some pointers to detect the limit before I pass it completely.

The gearbox TCU's have some decent logging capabilities and I captured a couple of runs showing the rear trans log at the top and the front trans log at the bottom. The white line is RPM, the Green line is VSS, Purple is Trans Slip and Yellow is Torque Convertor Slip.



I'm hoping that as the limit is approched rather than passed it will show by a sudden increase in either Trans Slip or Torque Convertor slip but not sure. Am I on the right track with my thought of monitoring the limits of the trans or is there really no way of knowing the limit until it just breaks? Is there anything else on the trans that would help to show the limit such as a abnormally rapid fluid temp increase etc?

The transmissions are GM 4T40e stock units.

Cheers,
Mike

Quite tricky to determine that I would guess, trans slip would be an indicator of clutches slipping(you'll need more line pressure to keep clutches firm), torque converter slip is a by-product of extra torque so that won't help. I found out the hard way with my GM transmissions, I had a 4L60e which shat itself 3 weeks after installing my supercharger, so a strengthened 4L65e went in, and when I stroked the engine a 1st gear burnout cracked the aluminium drum on that as it'll pick the weakest part but did not warn me in advance, I now have a 3L80 good for 1500hp so no more breakages for me, unfortunately no overdrive and it's manualised so it's a shitter on the motorway. Does the 4T40e have an aftermarket for better parts? i.e. shift kit, boost valve, clutch paks, servos, sprags etc. I hope someone else here has the same trans and can help you on that one.

Regards

Paul.

Hi Paul,

Thanks for the info.

There is quite a selection of uprated parts from the US for the 4T40e which will make it take 600+whp reliably. Just wanted to see how much it would take in stock form as it's a huge job to get the transmission out of the mini and also keep trying to push things on as little budget as possible

I'm planning on a spare trans to rebuild over the winter\next year with uprated parts (you can get it to about 400whp which is more than I would be running at my max power plans with just new torque convertor and clutch packs\bands kit at sensible cost) but didn't want it breaking before had some use out of however still wanted a bit more speed to get me in the 10's.

Cheers,
Mike

600whp, maybe, reliably, NO. Some people in the U.S say the 4L60e can be built to take 6-700whp but I snapped mine at 433whp, I had all the fan dangle parts but the ali drum cracked and blew to pieces(they do not make a billet drum that I am aware of), but in saying that it's the torque that kills trans more so. So a progressive nitrous system would be beneficial for trans longevity.

Paul

Prevention is better than cure as the saying goes, so I'd beef it up BEFORE you wreck it.

What times are you running now?

Hiya,

Currenly it's running 11.76 with 50hp fixed shot on the rear. Going to increase this to 75hp fixed for next weekend but won't go any higher than that until i'm on progressive (want to run up to 150hp once progressive but even then it will prob only be approx 300whp).

Over the winter will hopefully install the front engine nitrous and run that manually from the steering wheel once i'm in 3rd gear with 50 or 75hp fixed to help my 1/8mile onwards performance and eventually go progressive up to 150hp to run from 2nd gear onwards.

Understand what you mean about reliably at that power, I suppose it's more accurate to say that the uprated components are good for that much power (where the stock parts are pretty guaranteed to break before that) but that still doesn't fix anything else that may snap but as with most things when modifying it's luck of the draw

Cheers,
Mike

Hi Mike,with automatics one thing for sure the killer is heat..so with this in mind upgrading fluid is key as well as cooling. I feel these are things over looked even when upgrades are made. There are alsot of fluids on the market so beware of all the hype as many people sell the sizzle and not the steak sort of speaking...I guess thats advertising 101..lolol

I would if you havent upgrade to Amzoil transfluid to fit your vehicle specs as theres was the 1st trully synthetic and still the best IMHO. Coolers with fans on them as there are many on the market and one more thing is when running a aftermarket cooler disconect from the radiator cooler as this will add in putting heat into the fluid because of your water temps...if you go to a mini or max contoler I feel you will also add life and less stress on your tranmission even on small hits...I dont think you can have to much cool for the auto boxes is my opinion..also stalling the trans or running up against the convetor is another heat increase that is huge while this is being done. So if you need to do this waiting till the last moment to do it is important also.I have seen trans temps raise 100degrees in less then a second while stagged on the 2 step

If you have a arse whole in the other lane dicking about and i have seen this alot of people will continue to ride up against there convetor,this is one thing that I guard against and going in last will help with this problem if you can. If I have repeated anyones advice forgive me...good luck