I wanna build a 200Hp CB-80 Motor, what do i do.

I want to build a Group A GTti Motor??
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I went to the workshop on Saturday to see how the GTti was going with its rebuild!
The cage looks sweet, BUT

While the Sti was getting some new stoppers I saw my motor totally striped in the engine room, only to see the number 2 piston split in half (top to bottom) with a busted con rod and crank! Ouch! 5 years on the road and 2 years on the track have taken it toll.

So I want to know from probably the UK guy. What can be done with these motors's to get some real HP out of them with reliability? (I think in the UK the GTti was group A spec) here in Aust it only got to be a Group N beastie for the rally team's so there's not too much know how in the engine department here.

Brad Mifsud

Ross Mackenzie?

Ig

The car's at NRG..
I dont pay for labour(the car is sponsored by them), so why would I go to someone else ..
Plus Nick has built plenty of race car's but not a daihatsu. We could look at it as another turbo motor and go from there, but I want to cut a few corner's with a bit of know how on what a GTti motor like's and dislikes before we start

Brad Mifsud

call him and ask for some advice, not build it for you.

he usually gives it freely and is helpful!!!

He has raced the things so he may be of some help!

Ig

I see sorry
But Ross never raced them in group A spec's
can't you read ?
I will email him anyway

btw, got your email
thanks

redcharade

one set of custom billet steel i-beam conrods, on set of forget pistons and ring set, balanced and nitrided crankshaft, o-ringed block with copper head gasket, aftermarket computer that is tuned by someone who an idea not no idea and some other little things along the way. keep an ye on oil, water and exhaust temps. that is if you want reliability.

matthew slade

You can spend a fortune and have parts made, however this is not necessary. The Group A cars here, UK, could run 200bhp quite happily on relatively stock motors. I own an Ex-works Group N car at the moment and I have also owned an Ex-works Group A car previously. I have stripped them both and compared them, there were not many differences, it is predominantly done by the ECU.

I have just had a new CB80 short race engine built and we did the following:

Standard pistons, slightly skimmed for compression
Standard rods, balanced end to end
Standard crank, balanced (never lighten a CB80 crank!)
Standard balance shaft, balanced
Considerably lightened flywheel, balanced
Paddle clutch balanced
Uprated coverplate, balanced
Mig wire rings to each cylinder to prevent head gaskets blowing.

I have had a hybrid turbo made and fitted an Omex ECU, it is expected to produce 200bhp when the head is done.

The Group A cars ran an LSD and a close ratio gearbox too. The group A cars were rally cars and not race cars and essentially achieved their power from the ECU.

I have a set of homologation papers that I am slowly scanning, it is a very large document and will take some time for me to complete, when it is I will get it posted for general information.

matthew slade

FYI the Group A FISA Homologation Number for the G100 is A-5344 and homologation was valid from 01/10/1988. You might be able to track a set down from FISA or indeed from the 'Japan Automobile Federation', they prepared all of the paperwork.

Ig

Look's like another beer for you when you come over to sunny aust!

80% of what you said has being done so I will just make sure its all balanced!
btw, you said never " (never lighten a CB80 crank!)"

Why?...mate there bigger than a WRX crank!

have you done any major work to the head?

thanks boy's

matthew slade

You will see when you get the crank out that Daihatsu have already lightened it and balanced it a little. When you map your engine you will be able to rev it like a motorbike engine and a lightened crank will just snap, my race engine builder refused to anything other than balance the crank. If you want reliability don't lighten the crank.

When you have the crank balanced, have balanced on its own, then with the lightened flywheel attached, then with the clutch and coverplate attached. This will guarantee a very smooth engine.

I haven't done my head yet, but all it will require is a port and polish job, don't be tempted to fit larger valves. I wouldn't waste any money on cams either, stock ones will do fine.

When you have the crank balanced, have balanced on its own, then with the lightened flywheel attached, then with the clutch and coverplate attached. This will guarantee a very smooth engine.

I haven't done my head yet, but all it will require is a port and polish job, don't be tempted to fit larger valves. I wouldn't waste any money on cams either, stock ones will do fine.

Ig

there you have it people's just buy a GTti...looks like they come built of the factory with all the good gear! unlike those silly detom's...
you need to do head work. pistons, bottom end, valves, etc to make those silly buz boxes move! pfft!

CXTdreamer

The reason the STi's crank is thinner is that the boxer engine is inherrently more forgiving when it comes to cranks, so they dont need huge ones

matthew slade

And they don't rev into 5 figures.

come at me (boostjunky)

how about the pistons?????? they are only semi forged aren't they????????? i was thinking of puting forged pistons in my spare motor and working th f#*k out of it.......
if i am going to put them in would 40 tho oversized be ok?
i want her to handle big boost.......and have no worries

matthew slade

Forged pistons are not essential but always good for large boost, improved compression is also a must for reliability.

Be careful with oversized pistons, the waterways are very close to the cylinder bores, you could induce a weak spot, you will probably find that the block will only need a hone.

come at me

Thanks, one question how much can these motors really take???????????? are bolt on gear the way to go???????