Destroking the CG13DE to under 1000cc

[CMF_kiwibuilder]

Hello
My wife just brought a K11 1.34L and she is after more top-end power. She used to have a BZ-R Levin with a 180hp N/A 4age in it which redlined at 9,000rpm.

She has asked me to investigate in getting the CG13DE to rev higher and make more power.
So far I have a set of 1L Pistons which with my maths caculations should give me a compression ratio of around 11.6:1 which is good but now I am thinking about fitting the shorter stroke 1L crank with the longer 1.34L rods which should De-stroke itt.

Q1: Is the 1L crank strong enough with new rod bolts to take the 1.34L rods?
Q2: With running a twin webber carb set-up and a WRX style air scoup (basic ram-air) would the head be able to cope with the 9,000rpm I am planning to run the little engine to?
Q3: Valves/Valves springs would be able to cope with an increase in max rpm?
Q4: Would the rods be able to take the increase in rpm as the shorter stroke means they work less then a longer stroke engine?

Thank You
Aaron Nelson

 

[CMF_kiwibuilder]

Sorry some more information:
CG10DE Bore x Stroke is 71 x 63 with a rod length of 137.5mm
CG13DE Bore X Stroke is 71 x 80.5 with a rod length of 120.00mm

So: Hybrid engines could be:

CG13 Block with CG13de Crank and CG10DE Rods and G10 Pistons.
Hopefully give me a 137mm Rod Length with 11.6:1comp ratio and a stroke of 80.5... Im confused..

Rod Ratio:
divide rod length by stroke so:
137.5 / 63 = 2.1
120.00 / 63 = 1.90
137.5 / 80.5 = 1.7
120.00 / 80.5 = 1.49
So rod ratio with the longer 137.5mm rod in and the shorter stroke would mean a better 2.1 rod ratio (thats near F1 there)They say a Rod Ratio of 1.75:1 is perfect so the 137.5mm Rod in the 80.5 would be good.

Piston Speed:
Multiply Stroke x RPM:
63 x 8000 = 18.7m/s
80.5 x 8000 = 23.9m/s
So the Shorter Stroke of 63mm works less at high RPM.

Someone help me, my brain has stopped working!!!

 

[CMF_xsoarerx]

i would say thats a pretty interesting idea. i got no idea on all the stuff you've done but it looks the goods

but have you thought about installing turbo, or other engines? Ga16de, SR16ve, SR20de or even sr20ve which are 200hp stock?

 

[CMF_kiwibuilder]

I have though about a Turbo/super Charged but once you have had a high revving N/A engine there really is nothing better....

I heard swaping a Ga16de etc etc into it is more hassel then its worth. Plus I am only aiming for 130hp max when the cars stripped out with a couple of buckets only.

Sr16ve would work but fitting it requires a cert, if i stay with the engine I have i dont need to get it certified... i think...???

 

[CMF_frank2]

with a 1.3 crank and the longer 1.0 rods, the pistons would come out of the block aaron
and the 1348 rods share the same alternative partnumber with the 1.3,s on the nissan4u site
(same length ?)
i took a cammed 1.0 to near 9k, and it was fine (very smooth with no sign of valvebounce)
and the 1.3 with 1.0 pistons and a good inlet cam (current setup) pulls very well, but i would,nt like to take it over 8k tho !

frank

 

[CMF_MattyK]

Not sure I see the point. Losing 25% capacity means you have to rev 25% more to gain the same airflow. ie a 1.3 at 7000rpm would flow as much air as a 1.0 at 9000 rpm, and far more reliably and cheaply.

If you're throwing money at it you might as well make the 1.3 rev to 9000, best of both worlds. It's not like 80mm is a very long stroke anyway.

 

[CMF_nz_aj]

A few years ago I'd heard of a NA CG motor used in a RWD datsun rally car over here that revs past 10,000rpm & puts out somewhere around the 200bhp mark. Got a feeling it's a CG10 to keep within whatever displacement rules there are for it's class. The guy who developed the car is part of an engine mod business, typically things like polished knife edged cranks, porting developed on a flowbench, custom cam grinds, dyno tuning, and there was likely plenty of time put into it. EVLGTI should know more.

 

[CMF_kiwibuilder]

I know it seems like there is no point but I think it can be done.
Ok so the longer 1L rods wont fit.. back to the drawing board...

How big are the big end and small end in the rods? maybe a rod from a different engine may work.

You reved a cammed 1L to 9k, what cam were you using, what engine modifications did you use?

I am planning to run a pair of webber 45's DCOE from my old Ford Escort mk2 rally car.

Loosing 25% displacement is not really an issue because the low power the engines make stock. 48kw vs 61kw. Rev the smaller engine higher and with some caculations you should be able to make around 80kw at 9krpm. The 1L pistons and over 11:1comp ratio will make up for any drop in CC's.

Also the head will need modifications with vale springs to cope with the hi-lift cams. Anyone know the sizes of the valve springs and are they single or double type? If i can find an alternitave such as GSX1000rr or CBR1000RR springs for the head should coupe with the increase in lift and rpm.

Rod bolts are strong enough to cope with the increase in rpm? If not maybe need to find a an aftermarket supply.

The 4age rod is 122mm long with the 4age having a stroke of 77mm which would mean the piston does not go through the head and is 2mm longer and alot stronger. They are also light weight and able to take 9500rpm easy.
Just depends if it will fit the crank of the GC10de/CG13DE and the cg10de pistons

The fueling/ECU is not going to be an issue because its all going the webbers will take care of the ECU!! God bless old school tech

or am i just barking up the wrong tree and should look at putting a 20v 4age into it???

 

[CMF_frank2]

i had 272 piper ultimate cams in at the time aaron ( tho my autosprint cam is nearer to a "true" 272deg), some vids here
https://micra.org.uk/cmf/message/33327
the single springs have about 2mm left at 9mm lift before they get coilbound, but the exhaust throats are only 19mm dia, so anything over about 9mm of lift is pointless
i would stick with the CGA crank personally, and very high compression and with the usual mods

frank