Let's talk forged engines...

Hi Neil
From what i have seen while i was searching, forged rods and pistons, hybrid turbo, camshafts would start to play a part at the figures you are talking about, a really good head gasket and some top notch bolts to hold it all together, intake cooling is going to play a huge part as well, might be worth looking at water/meth injection also good for stopping pre detonation.

A duel clutch might be a pain, but running those kind of power and torque i think anything else would struggle.
I run a Quaiffe ATB in mine, that does not require any maintenance, it's a fit and forget unit, taking the gearbox out to carry out adjustments or servicing is a bit much as far as i am concerned.

As for servicing an engine running that sort of power, i would service every two or three trackdays, it's looking after the investment and for the price of 5ltrs of oil it's false economy.

As for a stronger gearbox, i am waiting to see others input here.

 

Hi Neil
Got the Quaiffe from demon t**ts on an offer deal, i have a 225 so no LSD as standard so can't say about the difference.

How much is the Drexler one as i need one for my project

 

I will give my ideas as well.

Regarding gearbox:
I think the M3RS can be a good option if it fits the chassis. Considering my 2.0dCi has the same gearbox in a M2RS chassis. This means you can get all the parts already from the Renault yard. With the hybrid turbo I limited the torque to 570Nm due to clutch limitations. Gearbox is living happily after the bearing swap. Also, if the engine allows, you can fit a 250mm clutch and flywheel instead of the 240mm petrol one. This give you a little more headroom in terms of clutch. If my idea is correct and the gearbox fits, you have gearbox mounts and axles already there, shifting linkages, clutch cylinder.
The M3RS gearbox shares a lot of components with the Renault Master one, so is definitely a sturdy setup.
If you go to the VAG gearbox, you need to do a lot of custom things.

Regarding clutch:
I run a 250mm clutch relined by me with a more sturdy organic material with a stock pressure plate. Next trip will be an uprated pressure plate, but that is a different discussion. Runs well to 570Nm of diesel torque. Also dirt cheap.

Regarding diffs:
The helical system between GKN, Quaife and Drexler is very similar. The differences will be regarding the amount of torque you push to each side in case of slippage and how fast. This is the result of the friction between the satellites and the case and usually can be tuned with friction shims and/or preload. I'm still sorry I hadn't enough time to tune my diff when I installed it (GKN one). I personally consider Drexler a better brand than Quaife.
If you consider fitting a clutch'ed diff on a FWD, that is a big task. Chances are you will run it way to stiff at the beginning and it will make the car extremely under-steery. You will need a lot of testing time to find the correct balance between preload, locking %age, ramp rates together with the level of power, traction, grip and skill you/your car have. And everytime you want to do a change, you need to take the whole gearbox out, LSD out, change setting, shim LSD, repack gearbox, shim the diff in the gearbox case, gearbox back on the car. Unless you run a race team, this is almost impossible to tackle. Servicing the unit after all this work will be a piece of cake.
If you take advices, drop this clutch'ed LSD street car idea completely!

Regarding fuel:
The main downside of the returnless fuel system is that it has the pressure regulator in front of the rail, therefore no way of controlling what happens with the fuel pressure in the rail. Also you need to consider that the fuel pressure regulator is a device which acts against the average pressure, but the actual fuelling of the engine relies on instant pressure. Easier said, when one injector takes a big gulp of fuel from the rail, the next one will run out of pressure. Also pulsations will be pretty big. So is not a case of finding a bigger pump, is about the ability to control the pulsation.
Around year 2000, Honda installed on the Type R returnless fuel rail a physical damping device which was nothing more then a spring loaded volume filled with gasoline. That worked pretty well and may be a solution for mild to hot returnless setups.
But return system is definitely the best option if spec'ed correctly.
Swirl tank are a big no-no in a street car because they tend to heat the fuel a lot and run the risk of bubble trap into the pipes. Been there, done that. Perfect for a circuit car or drift car althou'.

Regarding rest of setup:
The turbocharger (frame size, A/R, trim...) options needs to go together with the requirements of the whole package, together with camshafts, VVT phasing, back-pressure on the exhaust, pressure drop on the intake. This is a very lenghy discussion on it's own.

Just my 2c. Happy to discuss in a constructive matter further.
S.

 

Wow, you just got me started.

Clutch:
Main duty is to transmit torque. But, we need to make a difference between the engine torque and the resistive torque. Also there is torque rise rate which is very important in clutch discussions and always missed. So abrupt torque inputs or big differences between engine torque and road loads is what makes a clutch slip.
Without going to deep into physics and formulae (can do this also if needed), main parameters that affect max torque capability of a clutch are:
- friction surface size
- friction disc diameter
- friction coeff of the material
- clamping force of the pressure plate.
Improving each or any of this will improve the max torque.

Friction surface size: (consider friction material is a round circular patch)
- obviously the bigger the surface, the more contact patch to do the job. This can be obtained by increasing the outer diameter of the disc or decreasing the inner diameter of the disc (you grow the width of the friction disc or by adding multiple disc (this is why there are twin disc, triple disc clutches)
Friction disc diameter: (consider friction material is a round circular patch)
- even if you keep the same area of friction material, because the torque is a circular movement force, the further you go from the rotation center, the greater the lever is (like using a longer wrench)
Friction coeff of the material:
- easy one, bigger the coeff, more torque. Organic material is first followed by kevlar and ceramic at the end. To keep things short, you should still with organic. Good drivability. Kevlar is not an option because it cannot heal, once you burn it, stays this way. Ceramic has the highest coeff, but very jerky engagement. I would stay away.
Clamping force:
- the tougher the pressure plate, the better, the disadvantage is a heavier pedal.

Another very important point is to keep clutch cool. As cool as possible. What happens is that coeff of friction drops with temperature, so the hotter the part, the least torque will take. This is why after 2-3 hard start, a clutch can slip. Drive it until cools down and then doesn't slip again.

This being the theory, my suggestion was to go to a 250mm 2.0dCi clutch (check if M3RS still has 240 or 250, otherwise already done). This addresses the first to points (more material and bigger diam). Also I can suggest you where to get the best organic material available, so you have street-able engagement and ~0.25 friction coeff (best for organic).

In order to achieve this, you need to see if you can fit the diesel flywheel. The clutch is then plug and play and definitely the gearbox fits.

Diff:
I used Drexler in FSAE competitions and worked flawless, never seen on Renault world.

Let me know if further details needed.
S.

 

Kept my red stock engine stock turbo rs250 over my gtx28 forged Megane. Just preferred the way it drove and I honestly don't think the Megane needs more power. If mine goes bang I may go for forged and hta30 but until then chassis mods tyres and track days is where my money is going

 

Regarding general engine spec.
Engine is a big air pump. You want to pump as much air as possible. More air means more power in some limits, but lets consider it for the moment.

In order to move the maximum amount of air, you would need high pressure on the intake and vacuum on the exhaust. Obviously impossible. So you need to live with high pressure on the intake and as close to atmospheric on the exhaust. But on a turbocharged engine, this is still not achievable, because you have a turbocharger on the exhaust. Park this idea for the moment.

Turbocharger is also a air pump. If you take the turbo side only, that needs as high as possible pressure pre-turbo and as low as possible pressure post-turbo.

If you put both idea together you will realise the trade-off between high pressure pre-turbo and as low pressure post engine as possible.
This is one of the most important trade-offs in a turbocharged engine when you select the turbo and the end performance of that engine.

Changing the exhaust line, just helps with the post-turbo low pressure. The other side of the story is the turbine size, A/R, trim, flow capabilities.
I think talking about a certain turbo is too early. I would start with the requirements you have from the car and that shouldn't necessary be a power number, should be a general experience and usability range.

To answer you another question regarding VVT deletion. VVT gives you more overlap at demands which helps with turbo spooling. So good thing to have. You think about deletion when your valve springs are so stiff that the oil pressure in the VVT in not high enough to control the camshaft position or when your engine is accelerating through rpm range faster than the VVT can go back to no overlap position. I don't think is your case in either direction, so I would keep it there. Tuned properly can gain you more then you loose.

Let me know where you want the discussion to go from here.

S.

 

I am not changing from a standard LSD, i have a 225 that is not fitted with an LSD, i had the box rebuilt and a Quaiffe LSD fitted while it was apart.
I now have a mk3 250 engine and gearbox that i will be fitting over the winter, the 250 gearbox is a non cup box so it has no LSD, i was going to take the Quaiffe diff out of the 225 box and fit it to the mk3 box as i want to fit that as well (because it is stronger)
all i was wondering was, if it wasn't a bad price i wouldn't bother swapping it over and to be honest if it is £1250 or more, i would consider a brand new 250 cup gearbox as that is about £1695 with my discount.

 

Bulardas you are the man, many thanks for your input, so much information there.
I am only looking to get mine to run 340/350hp ish, don't want to spend to much on it as this will impact on the amount of trackdays i can do
my car is only really going to be used for trackdays, but i need to be able to drive it there and back.
I was basically thinking of running the 250 engine in standard form apart from brand new standard turbo, 630 injectors, charge cooler, cone air filter and a turbo back Scorpion exhaust system.

 

There is also a compromise. In terms on clutch, what you would like is a F1 arrangement of 8 disks as big as a CD. But obviously this is not possible. So you need to see what is the best compromise between clutch size and clutch and flywheel weight.
Good catch with the started. It is something that needs to be checked, but I think is not an issue. On the diesel I can install single mass flywheel of 240mm and the starter still fits. So I think the petrol case will be the same. Also cranksensor teeth needs to be checked in the same way. But to answer your question, the diesel flywheel has the face towards the clutch bigger than the petrol version.

I can weight a stock diesel double mass flywheel and cover and clutch if you want. Best thing would be to find a lightweight single mass flywheel that can work with the 250mm clutch and cover.

On the TTV side, I don't understand which twin disk they are coupling with that flywheel. I wanted to build myself a twin disc but I can't couldn't find the space inside the gearbox case. It can be done but the flywheel needs to be very slim. Maybe it would worth a question to TTV if they can adapt they've flywheel for the 250mm clutch.

Regarding diff, the Drexler will definitely feel more engaging than the stock GKN. When I installed my GKN diff (from a 250 Cup gearbox into my diesel box) I was a little disappointing by how mild it was. So my idea now is to either find another GKN (I know hard and expensive) or in case I do need to open the box again (hope not) to try to mod the GKN one to a faster locking / more locking behavior. On the track I would definitely love moded one. On the streets is just fine.

One interested concept you may need want to look at (no Renault option althou) is the Peloquin. It is a hybrid diff composed from a helical main diff but with some clutches and preload to act more like a clutch'ed one without the disadvantages of tuning and servicing the normal clutch'ed LSD. I used Peloquin on VAG platform and it behaves perfectly. This is the diff I would love in my car, especially a FWD one. I think I had to mention this one to have the diff discussion completely.


Edit: is Wavetrac the diff I had in mind, not Peloquin!

Regarding what Ian was saying, if I would have to choose, I was definitely put the money towards Drexler then a new 250Cup gearbox. The stock gearbox has crappy bearings which needs to be changed anyway.

If you really want to be bullet proof for a track car, I would install a cooling system similar to the rally M3RS version. This will keep you happy all your life, oiling and cooling in the same time.

S.

 

Cheers Neil
Well for a start 310 hp would be okay, but 350 torques sounds great, i have had someone offer me a hybrid turbo from a 250 he's on here but i can't remember his user name.
Your car isn't white by any chance ????

 

Ok, clutch topic:
You want something sprung (disc or flywheel) and organic material. So to have a bulletproof clutch you need the biggest surface you can get, the biggest diameter and a tough clutch cover.
Usually dual disc will not be sprung in anyway and definitely you will not have space for a dual mass flywheel so you miss the sprung part. Having unsprung'd clutch, organic material is not suitable anymore because you will heat-up the material very fast. This is the reason why most twin disc kits are made with ceramic pucks.

So for a street car, I would go for 250mm single mass flywheel with an uprated organic clutch. This is be the most streetable option. And in the end, you can limit the power a little to help the clutch cope.
But this takes us to a completely different discussion of why do you want 450hp for a track car? Having a 2liter engine, you will always have issues with spool and you will end up being slower than a stock mapped M3RS and your costs will be higher on the track due to brake consumption (you will accelerate much faster on the straights and then you have to brake harder, but in the curves or after the curves you will exit much slower due to turbocharger struggling to spool).

So as I was saying in the first post, that is the purpose of this project? Track, drag, bragging rights...
Let's speak a little about your expectations regarding this car and why you stopped at 450hp? So maybe starting from the end goal, we can do the part selection based on this.

What is the guy in Greece with the Peloquin? I don't know him. Do you have any details or link? In the end, if you can fit it somehow in the gearbox, should work without issues.

https://www.renaultsport.com/IMG/pdf/megane_n4_en.pdf (page 22.0 for gearbox cooler)

S.

 

On the Renault sport, I'm not speaking about that clutch. A b£&$t to drive it on the street. I was just speaking about the gearbox cooling setup.

S.

 

So you would run a cooling setup for the gearbox oil ?????

 

Hi Neil
I remember a long time ago there was a chap who wanted to go racing, the engine was a Rover v8 (cant remember what car it was) told the engine builder/tuner (i want all the horse power you can get out of it) they asked and tried to persuade him to have an engine built and tuned to his requirements for racing, but he only wanted the max hp, they built the engine ran it in and let him take it, after the first race he went back and complained it was undrivable, as far as i can remember (it's a long time ago now) it was close to £10k build, max 11.5k rpm but power started at 9k rpm, they ended up rebuilding the engine, dropped it by over 100hp with a very linear torque curve, he was on the podium for his next race.

big horsepower numbers are okay for the pub, drivability is the key, good spread of torque is the key.

 

that one of the main reasons for fitting a mk3 engine into my 225, it was going to cost a lot more to forge the 225 than the 250 cost and it's only done 32K miles, 225 has 118k on the clock, it's still a good engine but i don't want to push to far and be capped by the max torque.

When are you thinking about going to the ring ????

 

I have done both TF and trackday's, trackday's are soooooooo much more civilised, nearly booked the DN double event, if it is in next year i will def book that and another earlier in the year.
Up for a group event

 

Looking at the 2 graphs, the torque is very similar 350-375ftlbs on both, so the clutch life is not very different unless torque rise rate is not hugely different.

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Great info given by Bulardas but also alot of assumptions.

The meg 3 clutch is 250mm which will hold 390lb/ft when in good condition. When you go above that you'll start to struggle with driveability on a fwd anyway so i would keep it along those lines if i where you.

Regarding the power, don't expect to be much faster on track with that sort of power, only thing it will be is more savage driving. I'm a powerchaser so to say but i don't really do trackdays so i don't mind

If you do want the power/torque as above i think setup will be:
Forged pistons and rods
Catcams+valve springs
Nortech manifold
.63 gtx3071r
715cc ev14 injectors
Uprated fuel pump/return fuel system.
And pretty much everything you decide to replace when doing the build

 

I don't think is 250mm either because I looked deep into in trying to find myself a 250mm single mass flywheel and M3RS area was the first to check.

S.

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I don't really have something useful to ad, but I do know that German YouTuber "xthilox" used to have a Mégane RS with a Drexler diff and wider tires up front (255 IIRC):

 

Thinking last night, I realised I made a mistake thinking about a different brand of LSD than stated. Is not Peloquin the one I was thinking. Is Wavetrac. Looking today on they're website, they just added a Clio197/200 option.
Worth looking over how is different compared with standard helical.
http://www.wavetrac.net/technical.htm

Sorry for the mistake.
S.

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I'll physically check tomorrow, i've read it a couple of years ago but my memory might trick me on this one.

 

Not had a chance to measure yesterday but a google search does indeed seem to tell it's 240mm