Big Torque at Low RPMs

[SomeGuy]

Point is, it's bad and leads to failures.

I'll leave some reading material for those who don't know any better:

http://www.mazdaspeedforums.org/foru...ng-rods-33010/
http://www.mazdaspeedforums.org/foru...low-rpm-97145/
http://www.mazdaspeedforums.org/foru...rpms-no-74519/

The list goes on and on...it's well known that torque down low is what will destroy these engines. Generally you want to keep torque below 3000rpm at reasonable levels, so no 300+ wtq. It might work for a while, but eventually it's zzb.

[Kiyomi]

o this gonna be good.

[loki]

my car has been on a GT3071r for 2+ years now, with 400wtq at spool up. No issues so far.

[SomeGuy]

my car has been on a GT3071r for 2+ years now, with 400wtq at spool up. No issues so far.

At what RPM though? Post a dyno graph.

[loki]

June 2013

[loki]

April 2014

[loki]

and what it is now is undeterminded

[SomeGuy]

Well looky there though, you don't pass 300wtq until after 3000rpm...seems fine to me. It's graphs like these that are a bit scary:

[ricola]

Hey! That's me!!! I'm famous

[Kiyomi]

Hey! That's me!!! I'm famous

thats not a good thing if your reading the info.

[MajesticBlueNTO]

Point is, it's bad and leads to failures.

I'll leave some reading material for those who don't know any better:

http://www.mazdaspeedforums.org/foru...ng-rods-33010/
http://www.mazdaspeedforums.org/foru...low-rpm-97145/
http://www.mazdaspeedforums.org/foru...rpms-no-74519/

The list goes on and on...it's well known that torque down low is what will destroy these engines. Generally you want to keep torque below 3000rpm at reasonable levels, so no 300+ wtq. It might work for a while, but eventually it's zzb.

did you read the threads you linked?

DETONATION down low destroys the rods, NOT high torque or too much boost down low.

The car that drove you to create this thread has no KR in the range you reference. No knock = no detonation.

FWIW I delved into this awhile back to fight the "time under load" bending rods misconception. The advice not to lug the engine below 3k rpm comes from several sources.

Pre-fuel pump days: Fuel delivery is insufficient on modded cars, particularly in cold weather, low rpm boosting results in airflow that the pump cannot support and boom. Unlike gen2s, gen1s try to keep on trucking through fuel pressure drops, instead of going into a limp mode by dumping fuel and protecting the engine.

From pre-tuning days: The turbo spools very fast and most modifications make it spool faster, but the stock ecu targets afrs in the 13s and doesn't transition to open loop fueling targets fast enough so detonation occurs and rods are bent.

From load cap days: Depending your MAF calibration it was possible to exceed the load cap with the stock turbo, especially at low RPMs. Exceeding the load cap = lean afrs and detonation.

I have talked to several very good tuners, a properly setup engine should have no problem with low RPM boosting. Torque is Torque, no matter the rpm. If the timing is too aggressive it will bend rods no matter the RPM as the pressure wave will hit the piston too early.

That being said, a MS3, particularly if it has exhaust modifications without a tune/fuel pump is not a properly setup engine. Even a stock engine in cold weather is not really properly setup so the advice not to floor it below 3krpm is good.

It's all detonation. Cylinder pressures spiking drastically BTDC bend conrods, not boost.

Lugging = the engine shuddering when at too low RPM.

I have an engineering degree, and I'm telling you the stress on the conrods is MUCH higher when detonating than just boosting at low RPM.

As I was poking at in the thread it's just simply management of the torque peak and avoiding knock, independent of the RPM.

I tuned my K04 to spool as soon as possible, and do the same with the BNRS3, I just keep the torque peak below 400, and only add timing in areas where the boost cannot make the desired torque alone.

If we were seeing bearing failures it would point more to a low rpm loading issue where the motor was loaded up before the oil pressure was sufficient.

Zigatapatalka

Woah old thread is old. The principle still applies - too much cylinder pressure and a lot had to to with the gen1 OEM tune/mapping that generated detonation before we had tuning solutions.

[SomeGuy]

Did you read your own quotes? Too much cylinder pressure...yes detonation is one way that this happens, the other is too much god damn torque. Plus I don't see a log to prove that there is no KR or any other issues. Clearly tuned on the dyno in controlled conditions represents the real world and he'll never ever see KR ever right? These cars are on borrowed time pushing that hard that low, it's only a matter of time before they let go.

Also, a huge spike at spool up and then dropping way off isn't a nicely driving car...I'd much prefer a smooth continuous surge of torque and not some massive peak because someone doesn't know how to tune a smooth spool up.

[murdaspeed]

Post a dyno sheet from your car to show us how its supposed to look.

[SomeGuy]

Here this is from a couple weeks ago, 3 pulls back to back, both 3rd and 4th gear...nice clean strong pulls. Notice how the torque comes up smoothly at reasonable revs and stays strong through the bulk of the midrange.

[SomeGuy]

Just want to add, this isn't a me vs them thing. This is a genuine concern for these people who are getting tuned and having a shit ton of torque risking their engines. @S.F.W. suggested that I start a thread to raise the concerns. I've never seen anyone else tune this way, the general consensus out there is minimize torque below 3000rpm, so...

[betterthansx]

That looks to be the type of tune you would want for the track. Progressive rather than one lump and it dies. I read some of the thread that you linked to, but I am at work so I didn't get to read it thoroughly.

How do you tune it to come in later? Is it altering the load targets, throttle position, boost? Is this only a problem on the K04 as the bigger turbos naturally spool a bit later?

[SomeGuy]

Really simplistic it's a matter of setting boost/load/wgdc where they need to be to get the curve you want and then to get it smooth using the dynamics tables to really dial it in (amongst a few other things).

Bigger turbos do naturally spool later (see loki's turbo) but mine is still a k04 but it comes on very progressive and then keeps hauling...I still have some left in mine to make more power but haven't been mucking with it lately.

[crasth]

Wouldnt the tuner be able to control it? I mean in the case of @ricola that was tuned as i saw in other thread recently.

[SomeGuy]

Wouldnt the tuner be able to control it? I mean in the case of @ricola that was tuned as i saw in other thread recently.

Heck yes...the tuner should easily be able to control spool up for the most part with the map. Obviously there's spring pressure (~10psi) so you'll always have that as your lower boost limit, but otherwise they should be able to keep your main spooling at a reasonable RPM and without such a drastic peak.