Help with the ultimate KR tune-up...

[Akinesis]

OK, so I've had my 'Rocco for around 18 months now and in the next couple of months he'll progress in leaps and bounds with an FIA-spec roll cage, a change to FIA-spec bucket seats and harnesses, stiffer springs, semi-slicks, just had new wide-wheels, fire-system, an alley fuel-tank with swirl-pot, revamped alley-dash with push-start and a new steering wheel. In fact, I'm going to start a project thread when I get home 'cos I think he deserves it! But I am mostly excited about the new KR engine I now have.

At the moment I have an EX with Weber-carb, GTi cam, Jetex exhaust, uprated ignition coil and the standard airbox modified to a ram-air set-up. I've got to say, this is a sweet engine with very good acceleration. I didn't want to spend a great deal of cash because I knew I would be upgrading to a valver, which I picked up from MarkH the other month (cheers, chap ). So, here is the list of mods which I will do:

- Port and polished head
- Race cams
- Lightened Fly-wheel
- Stainless manifold (will look into the best type at purchase time)
- Will probably keep the Jetex 2.5" unless someone can tell me one that will be SIGNIFICANTLY better (like, does a straight-through work better on a 16v, or is it still good to have back-pressure??)
- Use the 8v gearbox (shorter shift!)
- Possibly an up-rated clutch (the current is standard but brand new - is it worth upgrading???)
- Adjust ignition timing to suit Optimax fuels

But what is really on my mind is the following... FUEL/AIR DELIVERY!!

What to do?? As far as I'm aware there are 4 options:

- Standard ECU setup (with re-mapping and professional set-up, performance-induction, etc)
- Twin Weber 45 Carbs
- Bike Carbs
- Throttle bodies

None of the above are out of my price-range, even though I'm aware that the throttle-bodies could cost me up to 2,500 sheets. But if spending 2.5k on throttle bodies will give me, say for example (and only an example!), 200bhp and spending 1k on the ECU will give me 195bhp, then the ECU route it is! I will mention that this 'Rocco is a race car, not a road car - so noise/emission/etc issues isn't so much of a big deal!I also need to consider how hard it is to keep carbs in-tune with the varying air pressure/temps.

So, what do people think is the best ECU replacement mod (if changing from the ECU at all)? And have I missed out any other mods that would nudge up the BHP/Torque? I'm aware that a 2.0l bottom end would help, but anything over 1800cc's bumps me up into a race-class where 300-400bhp Evo's and Cosworths dwell, and that will leave me at the back of the pack! Also, I've thought about up-rating the pistons for lighter ones, but is that really worth the Quids Vs Power-gain?

Many thanks for your input

[Brunty]

I've got a KR in my race car, the build thread is here

The basic engine spec is pretty much all you can do with the 1.8 KR...

Bored out 0.5mm makes 1800cc
Forged pistons
Steel rods (Arrow)
ARP bolts
Light flywheel
Helix 4 paddle clutch
Seriously ported head
Piper race cams (320M, 290deg in and ex. The head needs to be machined to accept this cam due to the high lift)
adjustable solid lifters (Newman)
Weber DCOE45s
Supersprint stainless 4 branch
Exhaust is custom 2.25" (Your Jetex will be fine, they are straight through)
Running the standard VW "ecu" at present until I sort out the Megasquirt box

I think that's about it. Running around 170bhp at the wheels and have a strange misfire at 4-4.5k rpm that no-one has been able to suss out. Hoping the megasquirt will sort it.
Being in a light car it is fairly quick, in a quick test it was easily as fast as a stage 1 mk3 Scirocco with about 250bhp@flywheel.

[Chaps]

Brunty,
Has the lightened flywheel made much of a difference to acceleration? also what Compression Ratio are you running with those cams

[Brunty]

I've been running a lightened flywheel in all my cars for a number of years now. I can't say that I've really noticed much of a difference on their own. Coupled with lighter running gear it makes a small difference.

The compression ratio will be a fair bit higher than standard, but I don't know what it is.

[filmidget]

I could be wrong but I detect a little confusing between provision of 'spark' and 'air/fuel'?

'Cos you mention having the ignition optimised for high octane fuel, but then you mention:

" Standard ECU setup (with re-mapping, professional set-up, performance-induction, etc)". And you also compare "£2.5k throttle bodies" and a "£1k ECU", etc

But the KR comes with purely mechanical injection that can't be re-mapped, and even professional set-up is pretty limited. You can (could?) get programmable controllers to stick in extra fuel such as K-star.

If I have got the wrong end of the stick, please feel free to tell me to 'sod off', and ignore the waffle below.

Otherwise I think you need to think more holistically - ie what's going to work best together...

eg the std (ecu) ignition could be used with the bike carbs or aftermarket programmable fuel injection ECU, or conversely a fully programmable ignition ECU could be used along side the mechanical K-jet fueling - all of which could be made to work, but might not be optimum performance or value.

IMO:

If you are going for bike or sidedraught carbs, then you could use the std ignition ECU, but programmable would be better.

BUT if you are going to the trouble/expense of programmable ignition, and you have a healthy budget, you may as well go to programmable for the fueling to, whether using single or multiple TBs.

I don't know whether I would go DIY ECU (megasquirt etc) - see some success stories, but seem to see a lot of cases where it works, but the setup never seems to be spot-on in one or more ways.

What race series are you planning on running in? Crucially what do the regs allow?

[Akinesis]

I won't tell you to completely ‘Sod-Off’, Filmidget!

OK, dependant on what set-up I have depends on whether I adjust the timing to optimise for high-octane fuel – I know that this may not be relevant to every set-up but with a standard KR it can apparently increase the power by as much as 6bhp. And I tried to make my point clear about the Throttle-body Vs ECU set-up that it was merely an example. To look at it from another way, I was trying to say that I’m not prepared to spend (and I reiterate again – this is just for example ) an additional 1.5k for an extra 5bhp.

As with the KR – perhaps I am getting confused a little. I was aware that KR’s are mechanical injection, but I see a lot of ECU’s for sale on Ebay for them – is that the K-JetTronic (or whatever it is) and I don’t actually need an ECU? I want to steer away from electronics as much as possible, really – I love the mechanical tinkering. I was reading that with a good tweek and set-up, the KR can run over 160bhp before even changing cams, etc. That was the professional set-up I was referring to, and if there is no remapping involved then all the better!

With regards to the DIY ECU’s, Megasquirt, etc, I think I will steer clear of them for the moment. I’ve been having a think and have pretty much decided to re-build the engine to standard spec - I'll fit it and get it running first. I’ll then take it to get professionally looked at and set-up and THEN start considering TB's, etc. I’ll probably still port and polish the head, change the cams, etc, but as for TB’s and Twin-Carbs I’ll revisit them at a later date.

I’ll be joining the South East Motor Sports Enthusiasts Club (SEMSEC) who operate at Lydden Hill and Silverstone. I’ll be entering their Saloon and Sports Championship ‘Class 2’. My cousin is already a member there so it’ll be good to race along side him. I’m hoping to have my first race in September, with a trackday at Castle Combe in August to make sure everything is running sweet.

Brunty, if you don’t mind me asking, how much has that engine build cost you to-date??

Cheers, guys!

[Brunty]

With regard to the KRs "ECU", it's merely an ignition curve. If you are doing more elaborate stuff to the engine then the standard curve isn't really optimised. That's where your fully programmable ECUs come in, but they start at ~£600 +set up costs. For a full racing car they are worth it, and why I'm saving up for one.

I got lucky with my engine as I bought it with a burned out shell and rebuilt it with a new block... I estimate that it's about £5k worth. The con rods alone are £1.5k... But it'll rev over 8k when I've got the ECU sorted and probably deliver a bit more power when finished the way I want.