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Kane

Engine choice, regs restrictions

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Kane

I'm currently deliberating an engine choice for a car I'm putting together for hillclimbs and wanted to gauge opinion on the potential of a N/A engine versus a lower capacity turbo. The car is being built for <2000cc modified production class so other than the original block from a 205 mostly everything else can be changed as I wish. 

 

Option 1 - 2L XU using a diesel block and 16v head. I have an Mi engine in the garage so can make use of the head and other parts if going down this route. 

 

Option 2 - 1.4 TU using the 205 iron block with a J4/JP4 head. Option to use 1.1/1.3 cranks but not a lot of choice for stock rods/pistons. Max capacity is 1428cc with the 1.4 multiplier. 

 

I see there being benefits and drawbacks to both options. Starting with an XU you get a decent gearbox to begin with whereas the TU would need the MA box changing. Reasonable selection of stock parts for the XU and decent aftermarket options when developing the engine comes around. Stock TU items unlikely to be suitable not only due to the turbo but also the normal complications of making a 16v 1400. Aftermarket support similar though. I don't imagine the weight difference is going to be much once the BE box is stuck on the TU engine and all the additional ancillary parts associated with the turbo. 

 

If I'm honest I'm currently siding with the turbocharged option as it is something a little different from the normal 2L on throttle bodies route, plus the power potential is appealing. I do have concerns on how usable it is going to be however. FWD with shovels full of torque will be tricky to say the least, and ultimately could be slower than a mildly tuned XU. 

 

Any thoughts/advice would be appreciated. 

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Biggles

Cost & time ?  A mildly tuned XU I would have thought would be cheaper & easier/less effort than a turbo TU. 

Are there many turbo TUs out there ?  (I don't remember hearing about any but I may as well live in a cave as far as TUs are concerned.)  What's the body of knowledge like on what to do and what not to do (cams, boost, CR, etc) ?  Are you likely to end up doing all the development that's already been done on the XU yourself ?  200bhp at 6krpm and 200lbft at 2krpm should be quite maneagable with a good diff.

All that said, I like the idea of the turbo - just be aware voyages of discovery can be both rewarding and frustrating in equal measure.

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Kane

I'm in no rush as the chassis is the first thing that I want to get right before moving onto the engine. As for cost, I don't have the budget to expect to challenge the front running cars given how competitive mod prod is but would like to end up with something that isn't sitting dead last every meet. 

 

There are a number of turbo'd tu5j4/jp4's from what I can see online but nowhere near the amount of detail/knowledge compared to the XU. At least from what I have found that is. Plus I haven't come across anyone who has gone to the trouble of building a 1.4 16v and adding a turbo, possibly because of the difficulty getting the engine correct in the first place.

 

Despite this, I am still keen on exploring this route as an alternative to the norm. Stock TU5 bore (78.5mm) combined with a 73mm TU2 crank would give me a 1978cc oversquare engine with scope to hopefully use a decent sized turbo. Forged pistons for a normal TU5 should be suitable leaving only a set of suitably sized rods. 

 

 

 

 

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welshpug

there are a few Turbo TU's about, Matrin Lalorat Tweeqd Automotive is the quickest/most powerful one I know of, its a 1600 in an AX running around 400 odd BHP.

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Kane

A quick look on here and I've found he reached up around the 400 mark with water/meth spray and a squirt of nos. Not any more info other than a "forged jp4 engine". Do you know any more about it Mei? 

 

Does give some confidence that they can produce decent power. Even with a slightly lower capacity I'd imagine it wouldn't be hard to reach the point of diminishing returns with regards to usable power. 

 

 

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welshpug

not a clue Im afraid, you'd need to ask Martin that, seems to be some mad greek ones running a lot more power too.

 

as for the specific spec and what parts were used I wouldn't worry especially about that, rods and pistons made to your spec that are not a lot more money if at all over good stuff that may not suit your application, certainly wouldn't use anything like pec etc.

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Kane

What's the going rate for a set of Robson rods nowadays? JE pistons are reasonable through eBay's global shipping program by the looks of it, almost half the price of UK stockists. 

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petert

I was quoted 600 pounds recently. If I was making an XU, I'd use a steel crank and off the shelf K24 Carrillos, along with an XU 39.1mm height piston.

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welshpug

yeah mine were £585 plus postage.

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Kane

Does anyone know the differences, other than the bore sizes, of the iron TU blocks? The regs state that it needs to be externally identifiable but if it's a case that the same castings were used throughout the range with only the bore sizes changed then there would be no benefit boring out a tu3 block from a 205, other than fresh bores I guess. Tu5 blocks would likely be easier to source but may be worn. 

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