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HybridZ

200+ WHP NA build


middleagedcrazy

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  • 6 months later...

Some combinations of parts work exceedingly well together, others don't. Scott's engine with 40's on it should easily pick up 20HP if not more from the reduced pumping losses on the intake side alone. Putting him within 24 HP of a 3.2 with 44's--you would THINK the big carbs and 3-400CC's would be worth more than that on the Benchracing Theoretical Scale!

 

AGAIN, it's the combination of parts, not picking numbers out of the air that are based on nothing more than theory. It doesn't work like that except on the benchracing interwebs.

 

In Scott's case, he came up with similar assumptions as you did. In the end talking with a head porter and a cam grinder he came up with a 2.8 at 0.040" over that twisted a set of SU's to 182 hp at the rear wheels at 6500 rpms or less with less CR than he thought he 'needed'.

 

 

 

 

I totally agree with Tony D's "it's the combination of parts", everything complements each other.

 

Details on my L2.8 build:

 

f54 L28 bored .020 over cast flat top pistons, stock crank, stock rods, arp rod bolts.

 

N42 head, stock valves, combustion chambers welded and ported by Slovers 44.1 cc chambers, Fel Pro head gasket.

 

Isky custom grind cam 540 lift, 270 duration. THANKS TONY D for the Isky tip!

 

Pacesetter 3 into 2 header with MSA 2 1/2in exhaust kit.

 

280zx distributor, MSD II coil.

 

10.25 to 1 comp ratio, 7000rpm red line, 91 octane gas.

 

SU's with SM needles made 190.7 at the wheels, on the same dyno and no changes except carbs,Weber 45's, 38mm chokes made 214.6 hp at the wheels and 198fp torque.

 

 

 

Honestly, this combo has far exceeded my expectations. It has a mellow idle at 1000rpm and pulls hard from 4400 to 7000. Super happy with it.

 

 

Scott B.

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What was the tq lost or gain with the change from 40s to 45s?

 

Thanks!

He went from twin SUs to 45s, don't think there were 40s involved. Besides that, torque has be gained from going to properly-tuned 45s from properly-tuned 40s, otherwise power would drop...

 

If you're trying to get an answer about bigger carbs making less low-end torque, well that's not true. That is, unless you also decrease total intake length along with the carbs. The biggest factor here is the venturi size, as that is what incurs a large part of the pumping losses in a carburetted intake system. A bigger venturi equals less losses, to a point. If you have giant carbs on a tiny engine, you may kill your vacuum signal enough to make tuning very difficult.

Edited by Leon
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I totally agree with Tony D's "it's the combination of parts", everything complements each other.

 

Details on my L2.8 build:

f54 L28 bored .020 over cast flat top pistons, stock crank, stock rods, arp rod bolts.

 

N42 head, stock valves, combustion chambers welded and ported by Slovers 44.1 cc chambers, Fel Pro head gasket.

 

Isky custom grind cam 540 lift, 270 duration. THANKS TONY D for the Isky tip!

 

Pacesetter 3 into 2 header with MSA 2 1/2in exhaust kit.

 

280zx distributor, MSD II coil.

 

10.25 to 1 comp ratio, 7000rpm red line, 91 octane gas.

 

SU's with SM needles made 190.7 at the wheels, on the same dyno and no changes except carbs,Weber 45's, 38mm chokes made 214.6 hp at the wheels and 198fp torque.

 

 

 

Honestly, this combo has far exceeded my expectations. It has a mellow idle at 1000rpm and pulls hard from 4400 to 7000. Super happy with it.

 

 

Scott B.

 

ScottB your post is Encouraging for me. I have a similar combo with DCOE40 and got similar rwhp peaking around 6800

 

My next venture was a planned upsize to 45s or Mikuni 44s or maybe GSXR ITB setup.

 

Good to know there might be some power there.

 

TJ

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ScottB your post is Encouraging for me. I have a similar combo with DCOE40 and got similar rwhp peaking around 6800

 

My next venture was a planned upsize to 45s or Mikuni 44s or maybe GSXR ITB setup.

 

Good to know there might be some power there.

 

TJ

 

Good Luck TJ!

 

Tourque on the SU's was 180fp. I never ran 40mm DCOEs.

 

On the 45mm DCOE's the right venturi size makes a huge difference! Going from 34mm to 38mm gave a 16hp bump but had a small loss at 3000rpm. Thanks to Dave Rebello for the tip.

 

After reading Tony D's posts on the land speed car I'm wondering more about the benefits of ITB's. Wondering how much more power, if any, is possible. Of course dollar per HP gained at this point may not be worth it.

 

Scott B

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Seriously.

 

What would be the maximum likely HP and torque on a 2.8 fitted with SUs?

 

1:10 compression ratio and 91 octane.

 

Tractable cam (needs to idle at nearly 1000 rpm smoothly.

 

Go ahead and specify the best head and a good header.

 

I especially want it to produce torque at lower RPM, as this is to be mated to an automatic trans.

 

Somehow, I cannot imagine more than 175 hp. Which I'd never see, as the engine would need to spin faster than the trans would let it get to.

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People will come back with no "best" but I've asked the same question to Paul when he was building my head.

We came to the agreement to use a P79 slightly milled (around 1mm) with stock valves, ported/polished/shrouded + a street rebello cam with assymetrycal profile.

Below there's a F54 block with flat top pistons. Clearance between pistons top surface and head is also critical.

 

Only difference with your potential setup is the use of DCOE.

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24hp more with 38mm venturis , versus SU's carbs is 10 % more power, but a venturi is always a restriction in air flow, so don't expect get much more power without EFI ( Gsxr itb's like mines is the cheapest way to go, but jenvey, extradubody, and many other systems are available).

Just another advantage is idle tuning seriously improved with EFI

Didier

260 z 2+2

post-5139-030108600 1338281457_thumb.jpg

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