Plans For A Tiny Turbo Engine 1252cc

[Saveit 0]

Hi Guys,

 

So for next seasons Danish Endurance Championship (5 x 4 hour races) i am hoping to build a tiny little turbo charged endurance engine. It has to be around 1250cc. The reason for this is that i am racing in the 0-1600cc class and if you put a turbo on your engine youll have to multiply the actual CC by 1.25. 1252cc x 1.25 is about 1565cc which is close to perfect.

 

So as i see it i have two options, and within these 2 options there are some more options:

1. First option is to use the tiny TU1 engine and bore it from 73 to 76mm. A bore of 76 together with a stroke of 69mm will give me 1252cc. Is it possible to enlargen the cylinders by 3mm?
   
2. Second option could be to use either the TU2, TU3 or better yet the TU24 bottom end and use the 69mm crank from the TU1 engine. Question is will the crank fit inside these engines?
   

I would imagine the TU24 would be the best head to use with regards to flow?

 

Now my last question is regarding CR. What CR will i achieve by using either option one or two? I am counting on using Wossner pistons no matter what as i need 76mm pistons, so i could either go with turbo pistons if the CR if too high or high comp pistons if the CR is too low.

 

Phew, i think that was all for now

 

Stefan

Edited October 25, 2009 by Saveit

[cybernck 402 1 Cars]

Someone I know that races a 205 with a TU24 engine once told me that he'd found out that

the TU24 and TU1 share the crank, that it's just bore that differs. But this was a long time ago,

so I may as well be wrong! Easy to check though, just find out bore x stroke for these engines .

 

p.s. Doesn't Honda have a 1.25 liter engine in one of their older Civics?

[Galifrey 1]

fiesta 1.25?

[cybernck 402 1 Cars]

^ Ah, that's right! Honda had a 1.5 liter engine (or not ).

[Sandy 191]

TU1 crank is 69mm stroke, TU24 is 73.2mm stroke.

[Saveit 0]

Exactly. TU24 and TU1 does not share the same crank. Also they do not share the same bore either as the TU24 is 75mm and the TU1 is 73mm.

 

But what about durability and CR. Can the engine (or most importantly the crank) cope with the extra power? Now i am not looking at silly BHP levels. About 170bhp or more importantly 200nm at peak nm would do. And what about CR?

Edited October 26, 2009 by Saveit

[Saveit 0]

So did some calculations. If i were to use a TU24 engine with a static CR of 9.6:1 i would end up with about 9.2/9.1:1 when de-stroking it by using the TU1 (69mm) crank, which is perfect.

 

But can a standard engine cope with maybe 0.8 bar pressure from a turbo? 0.8 bar should be good for around 160-170 bhp from what i can tell by looking at other turbocharged TU engines (actually most of them doesnt even go as high as 0.8 bar).

[Saveit 0]

Guys? Fellas? Friends? Someone

 

..

Edited October 26, 2009 by Saveit

[welshpug 1,661]

how about a stock 1.1?

 

seems to have plenty of potential from what Tony Perks managed with what seems like a very basic spec here http://forum.205gtidrivers.com/index.php?showtopic=103709

[Saveit 0]

Yeah perhaps you could just go with a standard 1.1. But wont the extra 150cc make a difference when there is a turbo involved? Or is it just a matter of upping the boost a tad

 

Perhaps i should throw a head on with bigger valves or at least bigger ports. Which head would be the best in your opinion? 1.4?

 

But more importantly can the standard engine cope with the extra force and power?

[welshpug 1,661]

have you read the thread I linked to?

[Saveit 0]

Yes i sure have. Of course.

[dcc 855]

stated the xsi head found on the 106 xsi showed no gains in power and even felt flat when compared to a 1.1 head.

[cybernck 402 1 Cars]

Oh... I guess he was making that up then .

 

He did tell it to me while negotiating to buy my TU24 block .

 

 

Anyway, my advise is to keep things as stock as possible, so you'd be able to fix/replace things easier at a later date .

[Saveit 0]

stated the xsi head found on the 106 xsi showed no gains in power and even felt flat when compared to a 1.1 head.

 

Yes i see that, but here is a significant difference between an NA and a turbo engine. Is the turbo is forcing the air in to the engine i think it would be a benifit with the slightly larger ports. The ports may have been to big (and therefore the air speed will be too slow) for the tiny 1.1 engine when there is no turbo to force the air in.

 

So thats why i asked which head you guys think would be best for a turbo engine... But i guess i answered my own question now