Author Topic: 1043 G40  (Read 4010 times)

Offline G40supercharged

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Re: 1043 G40
« Reply #15 on: March 07, 2012, 11:24:44 pm »
The rev counter is on my 25 year old bike. It's a 4 cylinder 250cc twin cam 16 valve making 45bhp at 15000 rpm with the rev limiter set at 18500 rpm. It's about the same power as a 1 litre Polo but only 25% of the torque.

You can't simply increase the revs on an engine to get more power as the volumetric efficiency (i.e. torque) drops off so much at high rpm you end up with less power (torque x revs). For example the reason the boost apparently goes up at high rpm on a G40 is that the engine's ability to consume the air drops off rather than the charger spinning faster. It will make peak power at below maximum boost. (You should see a high boost figure on your 1 litre with standard G40 pulleys as it will be consuming 25% less air than a 1.3 at the same revs.) You can move peak power up the rev range with things like big valve head, suitable cam (3F?), and high flowing manifolds (3F and 4 branch). 

Offline randombadger69

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Re: 1043 G40
« Reply #16 on: March 08, 2012, 12:12:11 am »
This makes sense! Is peak power on your bike at 15000rpm?

Im not trying to build anything amazing that screams to 10,000 rpm. I just think it will be interesting/funny to see whats achievable with the short stroke.

It's a shame my standard pulley got broken en-route from germany. Will have to try an source something.

Offline PeteG40

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Re: 1043 G40
« Reply #17 on: March 08, 2012, 07:57:17 am »
can  probably supply a stock v belt pulley, if not then maxrpm have second hand ones for cheapish

Offline G40supercharged

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Re: 1043 G40
« Reply #18 on: March 08, 2012, 09:05:45 am »
This makes sense! Is peak power on your bike at 15000rpm?

Yes, peak power is at 15000 and then it drops off to the red line. The high revving engine was mainly a marketing gimmick as the power was limited to 45bhp by the Japanese learner laws (still makes the same power as an early 1960's Grand Prix 250 though).

Offline randombadger69

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Re: 1043 G40
« Reply #19 on: March 14, 2012, 09:34:31 pm »
Anyone G-charged a 1043cc before?

..Other than Phils comedy build!

I stripped out a 2G block. Which confirms the bore to be 75.0mm. I measured the rods and they are the same length as the PY rods.

Which makes me think all i need to change is the crank into a PY block to create a 1043cc with low compression?

Ideally i want to build a 1043cc turbo, but as i have all the gubbins to run it with a G-lader, im thinking of testing the water first before i invest in turbo componentry.

Just wondered if anyone else has had a play around with the 1L lumps and boost.

Spot the mistake :D

Of course everything measured the same as a 1272cc.. it is a 1272cc.

Pulled the wrong lump apart. It was the HZ lump I had sat there I meant to be checking! DOH!

Offline ereeiz

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Re: 1043 G40
« Reply #20 on: March 14, 2012, 09:52:57 pm »
lol! :D

Offline randombadger69

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Re: 1043 G40
« Reply #21 on: May 14, 2012, 12:47:44 pm »
Not sure this is going to work as i'd planned. I stripped out an HZ lump and had a butchers.

Compared the PY piston and rod to the HZ piston and rod. The rods seem to measure the same circa 122mm c-c. However the HZ piston is about 10mm taller from centre of gudgeon pin to face of piston than the PY piston.

Which if I did what i'd planned; PY rods and pistons on an HZ crank, then i'd end up with very little compression.

So I may have to use the PY rods on HZ pistons giving me 9.5:1 compression ratio :o

I may have my AAV engine apart and see what the pistons look like in that.

Need to get my hands on a dial gauge.

Offline Yoof

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Re: 1043 G40
« Reply #22 on: May 14, 2012, 04:18:31 pm »
And a few headgaskets....  ;)

Offline randombadger69

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Re: 1043 G40
« Reply #23 on: May 14, 2012, 10:43:53 pm »
And a few headgaskets....  ;)

That wouldn't be a problem, got plenty of these from my 1306cc build.


Offline djtez

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Re: 1043 G40
« Reply #24 on: May 15, 2012, 09:55:10 am »
interesting stuff!

standard pulley size will get you just shy of 8,000rpm on standard top bearing.

wouldn't mind hearing exhaust notes at 8k... build it :D

Offline randombadger69

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Re: 1043 G40
« Reply #25 on: May 16, 2012, 01:15:20 am »
Aah.. don't!

I want to, just we went and found a turbo...

I might have to put a stock 1043cc in with 2 headgaskets. A pattern BGA type copper oil feed seal on the bottom and a genuine type with a rubber oil main seal on top and a shitty old AAV head as it will go bang and i don't want to waste a good G40 head. (A camshaft I can sacrifice if it came to it, but exhaust valves.. ideally not).

Hmm.

Unless someone fancies machining my HZ pistons for peanuts?!

Offline Andy

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Re: 1043 G40
« Reply #26 on: May 16, 2012, 06:37:50 am »
Depends how much boost you run. Chris' 9.5:1 AAV lump seems to be holding up okay though I think he's around 12psi on a K03 for daily use.

Offline randombadger69

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Re: 1043 G40
« Reply #27 on: May 17, 2012, 12:46:03 am »
I'd probably only be using a standard pulley if i went with the 1043cc. What do they produce 0.7 bar isn't it?

Pesumably due to reduced capacity the boost pressure would rise?

Which in turn will increase charge intake temp.

The turbo we have looks quite large, I dont think that it would be a good idea on a 1043cc. Anyone used a KKK K14 turbo on a 1272cc block?

Offline willsalter1000

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Re: 1043 G40
« Reply #28 on: May 17, 2012, 09:31:48 pm »
ive turbod a 1043 by accident, ran it on a renault 5 turbo carb with a t25 turbo, sized the turbo for a 1272 so on a 1043 it didnt pull full boost of 18psi till 3rd gear, it ran a 16.7 1/4 mile. tbh i wouldnt bother wasting your time doing it, just use a 1.3 aav like i inteded to do first time around or a 1.4 abd