15 replies to this topic

[Corey]

After taking the car off the road for a month or so, having interior bits retrimmed and general tidying up to make it look the part I finally managed to get it back on. Had a good 2.5 weeks in it, with a 500 mile round road trip, playing with dart moor roads, and out most nights but didn't really expect to take it off so soon.  It all started 3 nights before dart moor, where sometimes changing up from 2nd it would either maintain or gain revs before releasing it into 3rd. It generally got worse fairly quickly, slipping more often and got to the point after dart moor where in 1st and 2nd it will crunch and try pop out when being changed. It's strange because with down shifting it's fine, and so are 3rd, 4th, 5th, and reverse (even tho 3rd was just starting to slip), but I'm guessing with each gear the clutch will get weaker in time.  So here is my debate. Having to drop the gearbox out to get to it is a rather big effort, and I want to be running more power than the current stage 3ish figures (turbo btw). So do it just drop the gearbox and shove in an updated clutch for the time being (considering the car probably isn't going back on the road now til march) or do I take the whole engine out and start tweaking it? If I'm to take the engine out then I was thinking whether i should swap it for an leh? As I want to be running around 350-380bhp and similar torque. I've heard that the let pistons and rods will withstand about 300bhp and 350lb/ft, but the leh has stronger pistons etc and better cooling system, and apparently are safe upto 400bhp internal wise? (please correct me if I'm wrong ) So I'm thinking that it would be a more affordable way than uprating the let pistons and rods etc etc.  I was thinking around 380bhp because then I won't really have to think about a traction control system, and it's not a stupid amount where it'll spin up to 3rd and what not, it's a nice point where the car is extremely quick but managable and reliable (I hope ). Current stats are: Z20LET (almost 70k) VXR Turbo (K02 I think?) VXR fuel rail K&N turbo filter 2.5" (I think) exhaust with sports cat Courtenay Stg2 remap (I'll be using them for further tuning) Bilstein Gas Coilovers Ap calipers (1 pot i think? /:) No cooling upgrades  -- Running 258bhp, 200.5 at wheels and 288lb/ft ^ this is all that springs to mind atm I know a bit in mechanics, I do everything myself where I can but will be getting help when it comes to dropping the engine and internal work. I dont have a budget at hand, I'll be buying bit by bit and once it's all done remap it once up Courtenay instead of traveling 6 hours away a couple times.  I have a rough idea of what to get, like high flow top hat, bigger pipping, bigger afm and injectors but would like some help as to what to consider and what's the best cost effective way of achieving it. If the figure I want isn't a reliable engine wise, then I'm willing to reduce it   So yea, any suggestions, knowledge, watch outs and just general help and info into what i should do will all be very much appreciated!!

[rob999]

I was thinking around 380bhp because then I won't really have to think about a traction control system, and it's not a stupid amount where it'll spin up to 3rd and what not, it's a nice point where the car is extremely quick but managable and reliable (I hope ).

I'm not so sure, I think that will spin some wheels up but it depends how it's driven.
There's plenty of knowledge on here, pm Nev for some advice.
Don't forget to factor in a CC

[zebwach]

Sounds like you are in a similar mind set to me a year ago when my head gasket started showing signs of letting go. Here I am a year later, 11k+ spent and still not got it back. Plus I already had the CC and paddle clutch which are expensive pieces of kit. I'm not trying to put you off, but things are almost definitely going to go wrong, deadlines slip and it end up costing you more than you intended. It sounds more like your gear box is letting go rather than your clutch, although for those levels of torque, you will need a 6 paddle clutch anyway. The levels of power and/or torque you are wanting will not be easily put down on the road in anything but dry conditions with sticky ish tires such as R1R's or preferably 888's. Have you ever driven a 'stage 4' VXT with around 300bhp? that 50bhp doesn't sound a lot, but I couldn't believe the difference in performance and power delivery when I went from 'stage 2 to stage 4'. Maybe worth a go in one before you go beyond, as the costs involved with going beyond 'stage 4' are enormous. Stage 4 you will need:- Refurbished gearbox (recommend BOT) Charge Cooler Uprated clutch I'm amazed you have lasted 70k without a new front rad. Probably worth getting that uprated while the CC is being fitted if you want reliability. I would advise some suspension and brake upgrades to deal with the extra power also. The above is not going to come in cheap bearing in mind there are also all the hidden costs such as lubricants, release bearings etc Above stage 4 you will also need At least a 6 paddle clutch Upgraded fuel pump 3 inch exhaust Uprated exhaust and inlet manifolds Larger turbo Larger injectors Engine rebuild inc rods, pistons, new bearings etc I would recommend a head refresh plus head work depending on how you like your power delivery. A quaif diff is advised to help put the power down at 350bhp+ I'm not speaking from experience now, but from knowing people with LEH engines,an LEH engine would be far far from safe/reliable at 350bhp+ with their rods. Yes, the pistons are good for 400bhp+ easily, but the rods need replacing. On that basis the engine would need stripping anyway, so you may as well use the one you have. The under piston cooling can be easily fitted to the LET, as I have had done to mine. I'm fairly sure that the crank is stronger in the LET than it is in the LEH also, which is another added bonus. Feel free to correct me anyone. Hope that helps, Zach

[Seb.F]

Remember as well how different the power delivery gets it's not like just sticking the S/C on an N/A and you get mostly the same characteristics but just 'more' of them, the turbo can get quite agressive and some have decided they didn't get on with how the power is delivered at that stage of tune.

[Nev]

Hi Corey,

It sounds like your gearbox is failing, not necessarily the clutch. I have a second hand Helix clutch cover for sale if you like, good for 345 ft/lb of torque (possibly a bit more).

I have recently tuned my engine up to 500 BHP and 400 ft/lb of torque. It costs a lot. Whether you want 350 BHP to 550 BHP it makes hardly any difference to the price/cost as the work + parts is approx the same with the exception of turbo selection and whether you have head work done.

If you want, I can build you an engine and/or install it with all the 101 other tasks that need doing.

I have written a copious blog for aspiring power seekers such as yourself. Please sit down and read it all - there is loads of info in it that will answer loads of questions you must have. If you've read all that and still want to go ahead, please feel free to give me a ring. I have a big spreadsheet with all the options you can chose and their costs and effect on the power.

Seb.F is right that power delivery is quite different to OEM, it will no longer be a smooth transition, you can expect a car of 'two halfs' - before boost and after boost are staggeringly different.

Nev.

Edited by Nev, 11 October 2011 - 11:56 AM.

[Corey]

I gave reading your blog a go nev, read about half of it including the spreadsheet and my eyes couldn't take anymore - it isn't good on an iPhone whilst at work I actually didn't realise how much work goes into it, considering what you said about 380bhp being the same amount of money an work I probably won't go ahead with that much power. Reason being I'm only 20 and taking on that sort of challenge when im not in the financial position to do so isn't exactly ideal lol. Perhaps I should think about upgrading to stage 4 first? As I'm pretty close to being there, only exceptions being CC, injectors, updated actuator and clutch (nessesary to upgrade from 2.5" to 3" exhaust?). My understanding from what some of you guys have said is that it can be quite a difference jumping from 258bhp-288lb/ft to stage 4 figures? I will still most likely install the high flow plenium and 80mm afm both with required pipping, as I figure this will help for a smoother delivery band. The clutch plate you have nev sounds good depending on how much you want obviously but I'll still need to purchase a clutch disc for it. I also still need to somehow determine whether it is the gearbox failing as you have suggested, but there must surely be something wrong with the clutch if it's slipping? But thanks for the help guys

[zebwach]

2.5 inch exhaust will limit you to 293bhp

[Nev]

I gave reading your blog a go nev, read about half of it including the spreadsheet and my eyes couldn't take anymore - it isn't good on an iPhone whilst at work

I actually didn't realise how much work goes into it, considering what you said about 380bhp being the same amount of money an work I probably won't go ahead with that much power. Reason being I'm only 20 and taking on that sort of challenge when im not in the financial position to do so isn't exactly ideal lol.

Perhaps I should think about upgrading to stage 4 first? As I'm pretty close to being there, only exceptions being CC, injectors, updated actuator and clutch (nessesary to upgrade from 2.5" to 3" exhaust?). My understanding from what some of you guys have said is that it can be quite a difference jumping from 258bhp-288lb/ft to stage 4 figures?

I will still most likely install the high flow plenium and 80mm afm both with required pipping, as I figure this will help for a smoother delivery band.

The clutch plate you have nev sounds good depending on how much you want obviously but I'll still need to purchase a clutch disc for it. I also still need to somehow determine whether it is the gearbox failing as you have suggested, but there must surely be something wrong with the clutch if it's slipping?

But thanks for the help guys

Going to 'stage 4' is deffo what I'd recommend initially and makes the car brilliant IMO for b-road bashing, though for big curves and straights 300 BHP isn't anywhere enough really. The big thing that you will notice about stage 4 is the torque as the CC allows for an aggresive map without having to artificially limit the turbo or ignition advance (which stage 2 and 3 does). With an EDS or Klassen inlet manifold you can easily expect 310 BHP and 360 ft/lb of torque, maybe a bit more if you tweak the turbo. Some guy in Germany made 330 BHP which is amazing for that titchy little turbo!

If your cluch is deffo slipping then you need either a Sach or Helix clutch cover + plate system (which is roughly good for 350(ish) ft/lb of torque). The 4 paddle plates will bite more than the 6 paddles ones. If you want my clutch cover which is in good nick give me a ring, I can also give you the part number for the plate that you will need to buy to go with it.

Where abouts in the country are you? If you are near Bristol I'd be happy to take you out for a spin, a couple of squirts at full bore will scare the living sh*t out of you (and me) and make you realise that 500 BHP is far too much to enjoy sensibly.IMO a happy medium for the road is around the 375 to 450 BHP mark with the minium of torque possible.

Edited by Nev, 11 October 2011 - 06:12 PM.

[Nev]

I should qualify that last posting however, that 500 BHP is wickedly fun in the dry and so manic that it ovewhelms my senses every time I try and get near 8000 revs - honestly.You cant really use 500 BHP sensibly, it's just fun to try and use it, if that make sense.

Edited by Nev, 11 October 2011 - 06:48 PM.

[Corey]

So with those tips in mind, and being able to achieve 310bhp and 360lb/ft (or there abouts) would it be safe to keep the engine standard or just replace the conrods? If you could part with the part number so I can do some shopping around I will let you know about the plate, as it's guna save me money tbh And I'm actually not that far away, about 10 miles away from Exeter in Devon, I think it's about hour and half away? Sounds like a brilliant plan, would love to feel how immense the power is, and also see if my face can catch us up once we've accelerated haha.

[Zoobeef]

So with those tips in mind, and being able to achieve 310bhp and 360lb/ft (or there abouts) would it be safe to keep the engine standard or just replace the conrods?

If you could part with the part number so I can do some shopping around I will let you know about the plate, as it's guna save me money tbh

And I'm actually not that far away, about 10 miles away from Exeter in Devon, I think it's about hour and half away? Sounds like a brilliant plan, would love to feel how immense the power is, and also see if my face can catch us up once we've accelerated haha.

Internals will be fine with 'stage 4'

[Nev]

As Zoobeef says, there is not any need to make internal engine mods upto approx 300 BHP and 350 ft/lb of torque. I reckon a standard Z20LET engine has a good chance of coping with 330 BHP and 370 ft/lb, though there must be a bit of risk. I think the key is not to rev it too much (ie over 6000), as the rods and bolts are the weakest point and acceleration (both compressional and tensional) on the rods has a square factor I think. Thus if you double the revs you quadruple the forces on the rods + bolts. If you wanted to be super safe for a powerfull stage 4 build over 300 BHP, you can just change the rods + bolts (from under the engine) fairly easily. Nev.

Edited by Nev, 12 October 2011 - 08:12 PM.

[Corey]

Ah I see! I think it sounds like a good plan of action really. I would be happy with just a stage 4 tune for a bit, but if I can get away with changing a couple engine internal parts and not the entire inside so I can get some more out of it then that's what I'll do! Then atleast I'm not spending stupid money I can't afford. So with the rods and bolts being changed, what would you suggest going up to? Safe for 350bhp and 400lb/ft? I spose the next weakest thing are the pistons If I remember rightly. Although I doubt the vxr hybrid turbo I have will go up to that /:

[Nev]

Id be totally amazed if you saw 400 ft/lb with a K04 turbo, I think 360 ft/lb would be its total max. TBH, you want the torque kept as low as possible to keep the car drivable. I think 350 BHP would be quite safe with OEM pistons and maybe fairly safe upto 375 BHP. To get over 330 BHP you have to change the exh mani, turbo, downpipe and oil/water feeds, so it suddenly gets expensive at that point. I'd recommend sticking with your standard turbo and see what you think. Loads of people think 300 BHP is enough for the car anyway, you might be one of them or you might get bored like I did and then progress onto a complex build.

[Corey]

Okay got ya! So I'll stick to the plan of achieving just over stage 4 figures, 330ish bhp and similar torque if I can, see how I go and if I get bored after a couple months then I'll think about progressing. Tbh i think getting to those figures from where I am now is going to be expensive anyways, considering I don't even have a Charge Cooler and looking at Courtenays website, it's going to be the most expensive part! (as far as I know they are the only ones that do it) What I'll probably do is go away and do some research, make a list and see what you think if that's cool with you nev? I imagine changing the rods is probably as hard as it'll get for now, and I can imagine that they won't be that difficult to change and would have a go myself I do appreciate the helps guys, everyone chipping in their tips and experience does create a good bigger helpful picture.

[Nev]

Hi Corey, Rods change is fairly straight forward, though clearly you have to places the shells exactly and torque the bolts up precisely. Whislt you do that, make sure you install the Courtenay blanacer shaft delete kit too. Feel free to give me a ring sometime (number is on my website). I am happy to chat and discuss all your ideas and give you some no nonsense info on what is cost effective. Am hopefully gettting 'Nipper' back on the road tomorrow, if you fancy coming up for a test ride sometime. Yes, the CC is the bigest bit of going to stage 4, the Pro-Alloy kit that Courtenay sell is a good item, expensive and time consuming to fit I imagine. Once in, though the rest of the stage 4 mods are easy. Nev.