HP or Suspension?

[philip_240sx]

Some facts:

1990 Nissan 240SX: PI of 54.6%
Intake: NIL (Class +1 mod)
Cat back exhaust: NIL (Class +1 mod)
4-1 Header: 2 PIP
F&R anti-roll bar: 2 PIP
Non-OE shocks: 2 PIP
Non-OE springs & ride height: 4 PIP
Total PI: 64.6
Class: GT4

I was considering ditching the header and replacing it with the OEM unit... a simple but crude 4-2-1 unit. This would allow me to use the 2 PIP's for non-stock alignment (more camber! :) )and possibly other mods.

Which would you choose and why?

[ctenche]

Definitely go for the suspension mods. There is significantly more time to be had in a finely tuned suspension than you can ever hope to get from a header. Don't even bother thinking about "power" mods until you got your suspension sorted out. We're talking seconds here vs. maybe a couple of tenths from a header.

BTW, you might be able to save 1 PIP by only using one anti-roll bar. Generally on FWD cars, you want a soft front and as stiff as you can rear. Vice versa for RWD cars (within limits of course).

[philip_240sx]

The 240SX is RWD. :)

However my aftermarket swaybars are quite stiff... I am hesitant to use a combo of OEM and aftermarket parts for fear of upsetting the handling.

I am trying to find some dyno charts for the header still, but I am guessing I get around 5-10 peak RWHP with them.

[haniforama]

I'd do both... Here's how:

Typically the top portion of the stock manifold is not the greatest restriction in the header assembly, it's the collector close to where the catalyst is located. Keeping the upper "header" portion the same, enlarge the collector as much as possible (somewhere in the 2.25 to 2.5" range) and perform the same enlargement on the catalyst.

The collector mod is free at the +1 level and the cat mod will cost you 1 PIP.

This will net you probably 75-80% of the header benefits while leaving you 1 PIP to play with your alignment.

Hanif

[haniforama]

If your car is not equipped with an LSD, i'd consider removing the aftermarket swaybars (reinstalling the OEM ones with fresh bushings), increasing the spring rates slightly to compensate. then install an LSD.

Everything is of course $$$ permitting.

Hanif

[ADAM]

philip,

i would ditch the roll bars...the stock ones are pretty good, and maybe instead try to increase your spring rates...and increase the camber

or ditch the header...and use the points for alignment..

(i have a stock manifold if you want to use it)

[philip_240sx]

Originally posted by haniforama
I'd do both... Here's how:

Typically the top portion of the stock manifold is not the greatest restriction in the header assembly, it's the collector close to where the catalyst is located. Keeping the upper "header" portion the same, enlarge the collector as much as possible (somewhere in the 2.25 to 2.5" range) and perform the same enlargement on the catalyst.

The collector mod is free at the +1 level and the cat mod will cost you 1 PIP.

This will net you probably 75-80% of the header benefits while leaving you 1 PIP to play with your alignment.

Hanif

All good ideas, thanks. :) IIRC the stock manifold is a 4-2 cast piece with a 2-1 'collector' made from mild steel tubing. The design itself seems better than what I've seen on other cars. It would be very easy to modify this... I may even fab one myself.

Adam: don't throw away that SOHC manifold!!! :)

The points would go straight into alignment mods: more negative camber!!! :)

Thanks guys!

[ADAM]

its bolted onto the spare ka24e motor in the 2nd barn IIRC

[philip_240sx]

O.k. what kind of camber #'s should I be looking for? Adam?

[ADAM]

i run -2.5 rear
-3.5 front

stock castor ...and toe

[ctenche]

Adam, how come you're running stock toe? Guess with that much power you're not worrying about turn in. You just get on the throttle :)

Seriously though, a bit of toe out will help turn in crispness considerably.

[ADAM]

i tried some toe, but it made the car real twitchy..and the car can be made to rotate very easily via throttle steer..

the car is very nuetral..

actually philips car is very nuetral as well i took it out lapping last year and it was very fun to drive the way it sits....i think a bit more camber and larger spring rates would really help...other than that its not bad at all...

[Shaman]

I use a bit of toe-out but it makes the car a nightmare on the road.

[ctenche]

How much toe-out did you try Adam?

And yeah, toe-out does make the car darty on the street, following every rut in the road. I'm not sure how that would translate your fat tires Shaman, but I'm sure it's an interesting ride :)

[ADAM]

1.5 deg

[ctenche]

What size rims and tires where you running? Sorry, I gotta convert to inches to relate.

[ScotcH]

Originally posted by ctenche
What size rims and tires where you running? Sorry, I gotta convert to inches to relate.

Yeah, it seems much more natural to say 1/8" toe out . What's the usual (as in more common) way to express toe?

[philip_240sx]

Heh, tires are another matter for me... I have to get some rims first.

I will prolly run similar alignment settings as Adam. It may prematurely wear out my street tires however. Fortunately it isn't a daily driver.

Anyhoo, I'm looking for a stock exhaust manifold right now.