175 DCI Megane RS dCi 175 - hybrid turbo discussions

Hello everybody,

I know there are around here a couple of guys running some hybrids in they're diesel cars. I would like to see what is everyone using (details like dimensions of the comp wheels or anything) and what results they are getting out of this. How much lag they got from this, how much power...

I'm prepared to go down this route and I would like to learn something from the general opinion before I take the plunge.

S.

 

Hello RSDCI225,

I'm trying to build a general knowledge database about this engine and how we can take more power out without the increased prices of reputable tuners.

Our turbo is a GTA1549LV (Garrett 770116-0001) in stock form.
There is also a GTA1749LV (Garrett 765017-0001) available from Laguna which you can fit bolt-on (untested the bolt-on-ess yet) and give you around 10hp like you are saying. The increased power is from the larger exhaust wheel which chokes the engine less at high rpm.
So basically, you just swapped for the Laguna CHRA rather than really make a hybrid? So you got to 223bhp and 520Nm.

There is another turbo even better which looks also plug and play GTA1752LV (Garrett 765016-0001).

So there are 2 turbos for our engine that you can mount easily and get some extra power without the increased price, from what it seems.

I already got a turbo from a Laguna which is a GTA1749V (765015-0001) and I hope it will bolt-on easy despite the fact is no L in the name. From the pictures it looked like water-cooled as well.
The plan is to update it even further to a 52mm compressor wheel. Or maybe even changing the exhaust wheel for a bigger one and a 56mm compressor. This is the kind of discussion I would like to start, which I hope it will not end for "go and buy from K-tec.." sort of thing.

My aim is to get to maximum 450Nm (limited from the ECU) but to keep this torque as flat as possible. Below is my torque desire next to the original car torque.



From here, I will calculate the air necessity and the boost to keep Lambda on the smokeless side. And then, to see what turbo fits my need.

I'm a big fan of diesel and I know this engine can do nice things if he gets the love he deserves. I will get an F4R only inside a Clio shell, so I will not go for a R26 too soon.

Any feedback anyone?

S.

 

I will start a build thread soon and I can assure you I will not pay 3000£.
And if you look on my graph, I will have less torque than you, so clutch soon be safe. In case I need a clutch, I will use a refurbished kevlar one. Anyway, I have to open the gearbox to change the bearings (classic 5-6 noise) install a LSD and see if everything is safe and sound. Also, I want to do some oiling modifications in the box to live a even happier life.
DPF and EGR are gone for good now.
Intercooler will come and the pipes. That is a must for my target.
Remap will be made by me, so no cost there.

S.

 

Hey CJ_RSport,

What makes you think the injectors are not big enough? I have an opinion about this, but I want to see others. How many degrees are you injecting now? What do you consider as being the limit? What fuel pressure are you running?

If you really want bigger injectors, you should look in the Renault Magnum truck. The nozzle should fit well our injector and the 140degree spray angle should also fit. Not 100% on this, but I'm still chasing it.

But please tell me, why do you think our injectors are too small?

S.

 

Hello Andy,

Definitely, this thread is not dead. I'm working on the car, so updates will be made from time to time.
One of my next big jobs will be the gearbox upgrade. That means uprated clutch, LSD, changing the noisy bearings for 5 and 6th and see what needs a little bit of love inside the gearbox. Is not that hard to find that our car runs a PK6 gearbox, the same gearbox like in the Meg III RS (250, 265, 275). So any LSD that fits those gearboxes, will fit ours with small modifications. I'm still trying to see what brand I want to put in.

About the clutch, I'm thinking of doing a uprated clutch myself by using some kevlar friction material for clutches (usually has 20-25% better friction coeff and is still very drivable as a daily) and a more powerful diaphragm spring (anything like 15-20% more). Is very hard to say if the X-trail or even the Master clutch is stronger or not. My solution is not necessary the easiest, but I like to do custom things on my car rather than paying the premium just because someone else figured out before. I don't want to go for more than 500Nm and the stock clutch should be good for 420-430Nm, so after the upgrade I will be very safe.

I don't have the DPF in place and I believe there are some friendly places around that will "miss" to visual check with DPF. I got the car with a MOT and DPF delete, so I'm not scared there.

I'm also messing a lot with my DCI, so please feel free to share.

S.

 

H&R springs review:
http://www.rsmegane.com/showthread.php?5153-H-amp-R-purple-spring-on-175dCi-review&p=59755#post59755

 

I also heard the same rumors about the axles, but we have to break them to find the limit. And to be honest, I don't really thing they are so weak.
The diff should cope the torque without to many issues. But if you are really concerned about this, find a OEM one and improve it's strenght. Superfinishing + shoot peening + cryo and you will leave happy after this. But maybe is just me that is trying to do everything better.

But the discussion about the diff and gearbox and axle breaking, goes to the discussion with remapping. In my opinion no one is doing a proper remap. They are just making the maximum torque the turbo is capable and that is for sure bad because our runs a rather small turbo which will make a lot of boost at low rpm and obviously, you will make some silly torque numbers there. And 600Nm at 1800rpm does not help you anywhere, especially in a front wheel drive with open diff. But this is the consumer way of tuning diesel cars.

I know I don't want more than 500Nm (which is still a lot), so I will keep things under control even if I could do more.
My plan is to run 450Nm with the stock clutch and a not very abrupt torque ramp rate and then go for 500Nm and better ramp when I upgrade the gearbox/clutch/diff.

S.

 

Hello guys,

Sorry for my misspelling. Our cars run a PK4-013 and the Meg III RS runs a PK4-018. So you are right RSDCI225.

But, you are missing a couple of points here. Most of our refinement (how you call it) in our engine comes from the calibration rather and anything else. Even if you delete the DPF and remap it for DPF delete you will loose some of this refinement. Not to say about installing uprated engine mounts or anything.
You have to understand that the diesel engine can provide almost instant torque if you are injecting now 2mg/str (idle) and next cycle you inject 50mg/str. But you will break a lot of things in the process. So, they had to calibrate a lot of filtering for how you pass from 2mg/str to 50mg/str.
The most annoying filtering we have is the raw accelerator pedal filtering. Even if you hammer the accelerator to the floor, the ECU goes from 0 to 100% torque request in 5 seconds (i know this number from inside the calibration, not assumed or anything). So the car will never start hard from a stop light or anything because of this. The good side of this exaggerated filtering is that even if you play funny with the accelerator, the car will still drive smooth. So, the smoothness of our engine is something that we can keep when we remap or throw away.

As a personal feeling, I'm annoyed about the excessive filtering and I lowered in my remap. I like a car that does what I request, when I request.

S.

 

About the clutch now and DMF vs SMF.

I will explain what is the difference between them both, so to be sure everybody understand it well.

In our normal car we have a fixed clutch and a DMF that means the flywheel has to parts connected with some long circular springs to take out the juddering when we leave the clutch and we pull from a stop.

The other option is a SMF which is a block of metal acting like a flywheel only, but the clutch has some springs on it to be able to take that juddering.

Now, if you don't keep this kind of combination, you will make your car unpleasant to drive.

The Sachs clutch from above (if they really sell what is in the picture) is a clutch for a SMF because you can see the springs on the friction plate.
If you put that clutch together with a SMF, shouldn't be that bad. You will loose some refinement just because the DMF has longer springs inside, so it can dampen more until you fully compress the springs, where the springs in the friction plate are smaller, so you have less dampening.

But if you put a normal clutch (OEM non-dampened version) with a SMF it will be very hard to drive indeed.


On the other side, we need to understand what gives a clutch the maximum torque.
You have to multiply the friction surface (where you have that friction material) with the friction coeff and multiply with the clamping force.

S * coeff * F = max torque.

So, if you manage to make the surface bigger, the overall temperature dissipation will be better distributed and lower than in the other case, but you will increase your inertia.
If you increase the friction coeff, you can keep the inertial the same, but you will increase the heat in the clutch and flywheel because more friction means more heat (just when you are slipping from a stop or over the maximum torque).
If you increase your clamping force (the radial spring for the pressure plate) you have the same inertia, you have the pretty much the same heat rejection, but you decrease your smoothness when you start.

So everything is about how you balance everything. I want to go to a SMF with spring friction plate (from Sacks or stock one refurbished with kevlar material) and a tougher radial spring for the pressure plate. I'm fully aware what I gain and what I loose - this is just my call.

Hope this thread will go to technical discussion and not to "you cannot do that man, go buy a Ferrari".

S.

 

And also we need to understand what makes a clutch slip.

Beside the driving flaws where you forget to lift your foot out of the clutch or just slip the clutch because you don't know how to leave a stop, the clutch is slipped by a combination of rpm increase rate and available torque.

Imagine you are cruising in 6th gear and pulling a heavy trailer. For the sake of the discussion, your engine has tons of torque. Suddently, you go WOT.

- If your clutch is capable enough, you will start to accelerate and the speed difference between flywheel and gearbox main shaft will be the same (means you don't slip the clutch).

- If the clutch is on the edge, you will only have clutch slip on low rpm area because the engine acceleration rate (how fast it climbs the rpms) will be higher at low rpm than at high rpm. So our clutch can hold the torque because is not slipping in high rpm but cannot withstand the acceleration rate. But if you are accelerating through rpm even faster, you will slip even more.

- If your clutch is under-rated, you will slip every time your engine is giving more torque than the clutch can hold.

So usually, you need a 600Nm clutch to run a 500Nm engine and to have an extra 100Nm margin for the acceleration ramps.

S.

 

This is a Sachs clutch for DMF:
http://www.factorycarparts.co.uk/sachs-clutch-kit-2in1-renault-laguna-2-0dci-20.html

This is a Sachs clutch for SMF:
http://www.sachsperformance.com/Sac...M1K-110-kW-;-09/2005-:::2_2292_2859_4232.html

S.

 

Gavin, is your gearbox making any whining sounds when you use 5th and 6th?

What route are you going to take with your clutch?

S.

 

To change a clutch??? What can be that difficult??? Is not a GTR with dual clutch transaxle gearbox. Is a normal simple manual gearbox like 80% of the cars on the street. You don't have to open the gearbox or anything. If you know to untight and tight bolts and you changed some clutches before in your life, shouldn't be that difficult...

I can do it in front of my house with some basic tools and a small engine crane in one day (2 people involved).

I recomand you to speak with Fred from BTM Performance. Don't know how far it from you, but he will definitely be able to sort it out for you.

 

Fred is hard to reach, but once you managed to do it, he will do a very good job.

S.