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PostPosted: Tue Nov 13, 2007 5:06 pm 
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Location: Saskatchewan
This is the part of motor building im not quite 100% confident in myself with, what I know is the 1.6 has longer stroke with weak rods and a poor rod to stroke ratio.

What I want to know is if there is a cure to the poor rod stroke ratio by perhaps having a taller piston with a shorter rod? Again, not quite sure im 100% on understanding it here, but only the 4agze rods would be good for the g13b motor as they are like 2mm taller than the gti rods, but still shorter than the g16 ones.

I would ideally like to have low 8:1 compression with a hemispherical piston, rather than a dished top to reduce compression. I will be using my gti head (ported, and 1mm oversize vales) on the 1.6 bottom end. If I can get less than 8:1, say 7.5:1 or maybe as low as 7.3 I will simply gear the supercharger a little more to compensate.

However, the purpose of this thread is to see if there is a low compression (using high compression 1.6/1.3 pistons maybe?) with a shorter rod to both 1) be a replacement to my 1.6 weak rods 2) fix the poor rod to stroke ratio of the 1.6 rods (thus trying to not replacing them with just forged 1.6's).

Or if I were to go the custom made rod route (which I have the option available, but more $$) what would be the ideal length and with what pistons? (obviously if I am going the custom route Id go for a bigger piston pin aswell, and if its custom I can go with any 75mm bore pistons and have the rods made to fit... that is if im paying the big money for the rods.... but if thats the case and I can get some oem ones from another motor as an upgrade and are actually stronger, I can save money by not paying for forged pistons.) I am running a megasquirt so anywhere between 7.3 to 8.3 would be my ideal compression range. shotting for the middle as the best

sorry to post this thread but there isnt any actual solid information on this particular scenerio. For what its worth I plan on making ~200-220whp with this car, it will have alot of torque with the eaton m62. I would like the bottom end to be good for a solid 250-300 though. Ive seen other big turbo builds on the 1.3's but I want the torque. Any information you can share for my idea needs would be greatly appreciated!!


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PostPosted: Tue Nov 13, 2007 6:06 pm 
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Quote:
Any information you can share for my idea needs would be greatly appreciated!!


Stop worrying about rod ratio.
Its not signifigant, and not a concern to 99% of people who build motors.
The stockrods are not the best, but not bad, either.
If you really want torque, use a turbo, not a supercharger.
Those are my thoughts

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PostPosted: Tue Nov 13, 2007 6:29 pm 
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Location: Winnipeg
Dito what Super says. The rod in the G16 is around 139 mm long...not sure exactly off the top of my head. The people who say it has a bad rod to stroke ratio are talking about the rod being too short. With a stroke of 90mm, that makes the Rod/stroke ratio 1.54, the Honda D16 that many tuners turbo boost to over 350 HP has a rod to stroke ratio of 1.52, or even worse than the G16 Suzuki. Chevy's very popular 454 engine has a Rod/Stroke ratio of 1.53, and many engine shops feel it's OK to make 496's with them with 1/4" stroker cranks and stock length rods....for a Rod/Stroke ratio of 1.44
My personal project is a G16 with the Honda D16 137mm long rod. (aftermarket Eagle rods)
I'm not at all worried about the rod to stroke ratio, even though i'm using a shorter than stock rod, and plan to use it as a turbo engine.


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PostPosted: Tue Nov 13, 2007 7:00 pm 
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ok that makes me feel a little more confident. Reason I went with the 1.6 is because the revs match the sc efficiency better, and the peak torque is lower.

But is there no other rod/piston combination I could use? What about the taller piston with the shorter rod, the total length from crank journal to top of the piston COULD be the same. But are there any concerns with having it configured like that? obviously im not going to spend a bunch of money if its not necessary, but forged rods are pretty pricey on suzukird even. I dont want to cheap out anywhere that will hurt me in the end


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PostPosted: Tue Nov 13, 2007 7:34 pm 
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It's a longer rod that will improve the rod/stroke ratio.
I'm not aware of any longer rod, shorter piston combinations that are availible for the G16 at a reasonable price. Custom rods, and pistons are an option, but the price would be scary!


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PostPosted: Tue Nov 13, 2007 8:46 pm 
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yeah I hear ya, but its not worth building if im going to destroy it in no time, might aswell spend that damage money now and not have it blow up. Ive talked with a few guys and they say the rods like to go BANANAS ;);)


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PostPosted: Tue Nov 13, 2007 10:30 pm 
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....and that's why i'm using a much stronger rod, availible at a reasonable price, even though it's a bit shorter, and makes the Rod/Stroke ratio a bit worse than a stock G16.


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PostPosted: Wed Nov 14, 2007 12:24 am 
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OK, now I'll give you my real advice.
Stop worrying about rod ratios, and piston combos, and build the fckin motor.

Stop listening to know-it-all re-tards that blabber on about such inconsequential bullshit as rod ratios, get out in the shop, and start learning for real.
Thats the best advice you'll ever get.
I know that, because it comes from me :-P
If you build it, and it blows up, I'll give you another 1.6

Thats far tamer than my original advice :-P

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PostPosted: Wed Nov 14, 2007 1:20 pm 
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suprf1y wrote:
OK, now I'll give you my real advice.
Stop worrying about rod ratios, and piston combos, and build the fckin motor.

Stop listening to know-it-all re-tards that blabber on about such inconsequential bullshit as rod ratios, get out in the shop, and start learning for real.
Thats the best advice you'll ever get.
I know that, because it comes from me :-P
If you build it, and it blows up, I'll give you another 1.6

Thats far tamer than my original advice :-P


okok ;) Its just I have 2 cars, a turbo sprint which I use as a work beater that I throw money at occasionally. and now im out of bolt ons, but this car was meant to be done cheap and for fun. My REAL car I want to make sure I do right so im asking nonsensical questions, but you are right, the only reason I was getting all worried and thinking about it is because of what ive seen on here and the comparisons some people have made.

So its all good, ill throw it together, I guess with some forged suzukird rods (as they are the cheapest.... forged is forged, im not making 400hp) and some forged pistons too. I want to run a 75mm bore and be ABLE to run upwards of 18psi on a 8.0 compression. I wont be o-ringing the block or doing anything to the crank, just bored at the machine shop here, drop some pistons in and throw the head on and go.




Since I dont want to post another thread related to pistons and ideally with a convex (hemi shaped) piston design, are there any pistons I can use with regular stock like g16 rods with the piston pin a little higher up maybe with a hemi top? Im not a fan of dished pistons, just personal non-preference.

I have never even had a g16 in my hands (hillybillyswift is a procrastinator :-P) but soon enough!

I honestly really need your opinions on what to go with for pistons here, Im aware I may have some clearance issues especially with a convex top, but hear me out. The head I will be running (initially) will be the stock 13b head off my 90 gti. Later, when I throw cams in it, I will have the head ported and have a valve job done with 1mm oversize stainless steel valves (from what ive read 1mm oversize gti valves in comparison are the same size as stock 16v SOHC valves, correct?) and it can be done so I might aswell, I dont think I will be converting to solid lifters.

Ok, so if what I read is true, and gti head on g16a block will drop compression to 8.5:1 (as per this thread: http://www.teamswift.net/viewtopic.php? ... sion+ratio). So that means if I were to go to 75mm, have some quench areas drawn into the head and use a thick head gasket, I should easily be able to get that down to about 8 (with the valves and cam I should STILL be under 8.2 atleast Im guessing?) so this is good.

Now since im already expecting to spend some money on pistons, and forged may not be neccesary with a good tune, under 8.5 compression and usually under 14psi I should be ok with some cast pistons or whatever. And maybe an OEM solution could be ideal.

Now im just searching for someone who knows something about other cars that I can look into. I'm guessing I cant just throw any pistons in there as there are so many differences, for the next sentance refer to this picture:
http://www.teamswift.net/album_pic.php?pic_id=529
but say I bought a set of 1mm oversize GTI pistons (assuming they are made?), since they are essentially perfect for the valve cutouts on the gti head this would be good!. However, just looking at the picture it seems the vitara pistons are slightly dished and hence me now thinking the gti pistons will be insanely high compression.

Seriously I need some guidance on pistons now. I dont neccesarily think forged pistons are neccesary, so maybe some cheaper oem-like ones are the better option and I can take them to get slightly machined if need be.

For the record ive determined im going to buy either of these:
http://suzukird1.com/catalog/product_in ... cts_id=149
http://suzukird1.com/catalog/product_in ... a7041993b0

but their site for the pistons doesnt give any specific info, especially if im not using a stock head:

low http://suzukird1.com/catalog/product_in ... ucts_id=30
high http://suzukird1.com/catalog/product_in ... ucts_id=31

If I select 75mm for the 1.6 and 8.0:1 compression pistons, what will I get.

sigh I feel so stupid


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PostPosted: Fri May 30, 2008 7:15 am 
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I know this is an old post, but what did you ever end up buying for rods and pistons? I only ask because I am in the same situation and am getting ready to build a better 1.6 bottom end for 10-15 PSI of boost. :mrgreen: It's easy to throw money at parts , but I'd surely hate to waste money on something I don't need, but I am ot the best at tuning and would prefer not to have a fear of incorrect tuning and KA-BOOM!
I currently have a 1987 Suzuki Samurai with a totally stock 1.6 16 valve junkyard motor in it with a Saab turbo running 7.5 PSI and it is unbelievably fast......for a Samurai. Now I just need the "formula" or "recipe" for a better bottom end. Here's a video of the Zuk before turbo:



Now it's so fast in the sand I need paddle tires!


Thanks for any help or input,

Sean DeVinney
"Insanity is Bliss!"


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PostPosted: Fri May 30, 2008 4:18 pm 
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I scrapped that project and am building the gti motor. Seriously, the shits not worth the hassle and costs for extra 300cc's of displacement. that money could be spent for better power adding abilities

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PostPosted: Sun Jun 01, 2008 8:10 pm 
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OK, well, looks like without an available GTI motor I willl continue to use the 1.6 16 valve motor in my Zuk. I will try to do what Baldurag did and run 15 psi on a stock bottom end...only with a copper head gasket to lower the compression then have a friend tune it properly. If that holds up then I will be pleased.

Thanks for the info.


Sean


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PostPosted: Mon Jun 02, 2008 8:36 am 
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I have a spare head that just needs 2 valve put in a cylinder, complete with cams etc

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1991 Swift GT Build G10 +25 psi + other goodies
1996 Metro Build QR25de swap, still undecided where to take it
the lolcar family


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