Quest for Torque

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JohnR
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Quest for Torque

Post by JohnR » Tue Aug 17, 2010 1:12 pm

I realize that most people are after Horsepower and this gives great bragging rights, but after searching cam swaps and dyno sheets everyone is after top-end. What I am after is a tire ripping street car and for that torque curve is KING. I want a maximum of 400hp. So my question is without totally sacrificing power what is a good combination of cams and degreeing to get the most torque? Is it worth it going to oversize valves and porting the head or are these again more for top end power? I will be ordering a GT3071 turbo, and custom building an exhuast manifold as this engine is in a 70 Datsun 510, From reading a tubular manifold will give better power gains, so this design will be implemented. Also chime in on A/R size for the turbo I am thinking .82 A/R.

Currently I have a KA24DE 0.020" over size Arias 8.8:1 pistons, AMS Sportsman rods, ARP Head Studs, Stock head and valvetrain. Megasquirt ECU. 3" Exhuast from engine back.

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Post by Matej » Tue Aug 17, 2010 2:35 pm

Have you already lightened everything that spins? Driveshaft, flywheel, pulleys, wheels, and whatever else you can think of. Those would be my first steps. :)
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Jordan Gladman
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Post by Jordan Gladman » Tue Aug 17, 2010 3:30 pm

A tubular manifold will give best gains up high and for most applications it is best, but if you're going for all out low down torque, logs are supposed to spool faster and give the bottom end.

I dont think it will be possible to hit a 400hp peak and still have tq figures anywhere near that down low. This just isnt the nature of a 4 cyl turbo engine... you cant have a turbo that breathes like crazy up top and still expect the required turbo to hit full boost at 2000 rpm. IMO, if you want maximum torque but you still want 400whp. You have to size your turbo to be outside of its efficiency range at 400hp. So pick a turbo that will barely get there. A GT2871R comes to mind. Even a GT2860R would do... I ran a GT28R and was able to hit full spool just after 2000rpm, IIRC I hit 283lbs of torque at around 2500rpm.
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Post by JohnR » Tue Aug 17, 2010 4:14 pm

I have thought about a GT2871 and still may go that way as it will spool quicker and give less turbo lag. However what if I went with a smaller A/R like .63 on the 3071 would that not potentially give me the best of both worlds? I did make sure that the rods and pistons used were lighter than stock. I just do not want to make a change that sacrifices torque. So adding any turbo gives more power but changing cams changes the torque curve. I will have to look into the manifold design. Becuase I thought that the tubular manifold like full-race as an example spools quicker?

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Post by R33E8 » Wed Aug 18, 2010 3:24 pm

I think it would have been better to go with high compression pistons (like 10:1) and get some good tuning done.. Maxing out a smaller turbo would be better for your torque curve than getting a more laggy gt30r.. I would also run some meth injection...

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Post by eazye2000 » Wed Aug 18, 2010 4:02 pm

GT2860RS with a .86ar hotside combined with 9.5:1 or higher compression tuned on E85.

/thread


But I know this isn't a perfect world. I think I said this on another post recently, but I got 10psi on my 2860RS at 2,200 rpm's. It was almost like driving a V-8 at times. But she fell on her face and quit pulling after about 19psi. She would pull all the way to 7,200 at 19psi. She could get like 22psi at 3k, but would fall off at higher rpm's. Hell, it would hit 28-29psi at 4k, but fall off quickly after that. (pulled my wastegate off at the track /madface)
With that said, I never dyno'd it. So I can't say for power what I was making.

So take that as you will. I now have a T2 flanged, 3076R with a .86ar hotside, and it isn't as powerful down low as the RS was. Still spools fast as hell though...

Ok, I'm done. 8)
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Post by RLM_RSX » Wed Aug 18, 2010 6:10 pm

i love my setup make tons of torque spools about 3000-3500 and is fully spooled at about 4000 and holds till redline
i have a full ams rebuild
arias pistons 8.1:1
k1 connecting rods
full arp studs
im sure im forgetting things
rebuilt the whole thing only thing i need to do is focus on the head work
valves, cams, adj. cam gears, and intake that kind of stuff.
and heres my dyno i had done at element.
clutch was slipping pretty bad in 4th and 5th
kinda suspicious if thats the reason for it flattening out so much.
this was at 18psi and definitely not its full potential some things i need to fix that arent quite right
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Post by s13grady » Wed Aug 18, 2010 7:46 pm

pm me
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street trim sleeper

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Post by JohnR » Wed Aug 18, 2010 9:21 pm

I love the info, First no e85 I live in Canada and 94 octane is the best I can muster. Also I am looking to go for power however I am looking to not give up what the engine starts with. So when I make an upgrade to the camshafts what is the best avenue? I know there are lots of choices for cams and degreeing them makes a difference. Also I have had the deck of the block machined and the cylinder head also. Although I was not looking to make a compression change this engine had been previously rebuilt. I am expecting compression to be close to 9.0:1. Although I said chime in on turbo A/R, I am not willing to sacrifice my goal of 300-400hp. I just would like to get the most low-end torque while hitting my overall goal. And yes I know I must give to get and that a 2871 will give more torque than a 3071. But as I mentioned I am not looking for my next modifications to increase torque tremendously if it even does increase, I just do not want to lose any torque that I already have. I think I have selected a power goal that this engine is capable of without having to make torque sacrificing modifications. So if I can degree my cams while using a gt3071 to get slightly more low-end before the turbo spools, yet does not significantly hinder the turbo from hitting said power goal that is what I am after. Also for my application is the 248 cam swap a good ideaor leave the stock bump sticks and just degree them appropriately?

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Jordan Gladman
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Post by Jordan Gladman » Thu Aug 19, 2010 9:42 am

This is my old 2871R graph, Ive also run a smaller GT28R and the power was even lower. I believe I hit 18psi at 2300rpm w/ that setup.

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Post by JohnR » Thu Aug 19, 2010 9:47 pm

Great power from that 2871 what was the rest of your setup for that dyno pull?
If I could get those numbers I think I would live with 300hp I did not think the 2871 would pull more than about 280. The torque would be great also what was your driving impression? Have you ran bigger turbos?

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Post by Jordan Gladman » Fri Aug 20, 2010 7:31 am

The biggest I ran was a GT3071R. I had run a smaller T3/T4 60 trim before it and I believe the T3/T4 made much better torque and bottom end. If you're running a GT30/35 + turbo, you shouldnt be expecting to make much power below 4K.

I know of a few people making 400whp with GT2871R turbo's. 310 is not anywhere near the peak on them. IIRC that dyno was done at around 18psi, I ended up daily driving that setup @ 25psi, probably more in the 350whp range.

As for the setup, it was a basic SOHC setup w/ cam and log manifold, nothing too special.
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Post by dakar318 » Mon Aug 23, 2010 11:58 am

compounded turbo set up :D

should be very easy after that lol!
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Now that turbo's have been discussed

Post by JohnR » Mon Aug 23, 2010 4:18 pm

I am also after info regarding camshaft selection and degreeing them in appropriately. I want the cams to maintain if not increase the torque curve. Is the best combination leaving the valvetrain alone or stock cams and degree cam gears, or aftermarket cams and degree gears?

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Post by sr20drag » Wed Aug 25, 2010 11:19 am

Holset HY35 for $300 BUCKS ON EBAY. I had a GT2871R and made 365whp at 21psi on a SR20. They are great turbos but they cost $1100 and are not rebuildable. The HY35 has a 9cm2(.48 ar T3) hot side and will spool just as fast as a GT3071R .82ar and make 400whp and 400wtq at 20psi.

viewtopic.php?t=49206

This turbo comes stock on 98.5-2002 dodge cummins trucks with an auto tranny. They are very durable at 20psi(not so much after that), and can be rebuilt at any turbo shop for about $150.

The turbo in my sig pic is a HX35. It made 411/340 with the little 2.0L SR20. It is the same as the HY35 except for it has a larger hot side and with that comes alot more lag but it's capable of well over 500whp at 30+psi.
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Re: Now that turbo's have been discussed

Post by ILuvS13s » Wed Aug 25, 2010 9:43 pm

JohnR wrote:I am also after info regarding camshaft selection and degreeing them in appropriately. I want the cams to maintain if not increase the torque curve. Is the best combination leaving the valvetrain alone or stock cams and degree cam gears, or aftermarket cams and degree gears?
If you are only after torque, stick with stock cams and degree them to a lower lobe separation angle, this will make your power fall off sooner though. If you are willing to compromise just a little on the location of your torque curve, then go with the BCV2's. They have a fairly mild duration and lift thats larger then stock. You will make more power then the stock cams and more torque, but it will be shifted down your powerband a little.

You can then get some JWT cam gears, and narrow your LSA on either of the cams you choose. This will make your torque curve more peaky and come on sooner, but it will also fall off sooner.

Also think about intake and exhaust manifold options. Longer intake runners will increase torque. The same is true with a turbo mani, but then you will compromise some spool. A ported large diameter log manifold will help you spool that snail quicker which will create power quicker.

You could also think about adding a 50 dry shot.

IM me if you need your question answered more indepth.
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JohnR
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Post by JohnR » Sun Aug 29, 2010 5:46 pm

That is great information it sounds like bcv2 cams degreed appropriately would be good.

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