Squat durring acceleration

[jimszx]

My 280zx is the first car I have ever had with IRS and it has a noticable squat durring acceleration. It is still stock, but I am planning a V8 conversion. My concern is with the added power of the V8, will this cause the z to squat to the point of rubbing the rear tires? I have read through the archives but hav'nt found and answer to this. I would appreciate any info you have to share.

 

Thanks

[Guest zfan]

You will only have problems unless you lower the car or run a much taller tire.

 

Mike

[Guest zfan]

Sorry, I should have said IF you lower the car too much!

 

Mike

[j260z]

if you are planning to go to a V8 you will want to beef up the rear springs anyway so the squat won't become that much of an issue.

[jimszx]

Thanks, the car had performance struts and springs on it when I bought it. ansd it sets about 1" lower than stock. It has 215-60-14 tires on it which are about an inch smaller than stock as well. Is this part of the problem?

[260DET]

Similar suspension to a 510/1600 IIRC where squat is accompanied by increasing negative camber, not good. There are some worthwhile mods which can be done to greatly improve the situation but out of my area of experience. Try a 510 forum? Sounds like a good project.

[Phantom]

If you are planning on doing a lot of drag racing you'll want to increase your spring/strut stiffness in the rear and soften it in the front. That will allow the front to raise - rather than the rear to squat - to help with wieght transfer to the rear wheels. Adjustable struts would be a good start before you change any spring rates. It wil screw the car for crooked track driving & also hurt the daily driving aspect some too. Only installing adjustable struts and then "returning" for each type driving will minimize that.

Another issue you'll be dealing with on the IRS when you get the additional torque is wheel hop. Z's are notorious for it and, short of adding traction bars or going to a solid rear axle, no one seems to have found a sure cure for it. My differential mount has been raised about 5/8 - 3/4" in an attempt to minimize it but has had only a little impact.

[Guest zfan]

I have not had any wheel hop at all since going to the auto transmission. I only had problems when I ran the manual tranny and that was at launch only.

 

I am running Arizona Z springs all the way around and Tokico blue hp struts all the way around.

 

Maybe thats why I cannot get the car to pull 1.50 60 ft.s.

 

Mike

[JMortensen]

I agree with Richard. Try 510 forums. I can tell you about the most prepared 510 that I've seen. This is all rear suspension stuff: He runs weight jacks with threaded adjusters out of a circle track car, roadster front springs, Camaro (what year I'm not sure?) rear shocks, slotted crossmember and poly trailing arm bushings, and has solid aluminum crossmember bushings. Also has adjustable rear bar, the kind that hang real low on 510s. I know the comp roadster springs also fit in the 510, but they are REALLY stiff, probably too much for a 510 but might be OK in a heavier ZX.

 

There's a LOT you can do to a 510, and all of it should be transferrable to the ZX.

 

The main thing for drag racing I would think would be the camber and toe change when the rear squats, which you could adjust with stiffer springs and slotting the crossmember. MSA has a pretty slick looking kit for the crossmember. Probably don't need the adjustable ride height or sway bars. Due to the semi-trailing arms, you'll never get the camber or toe changed "fixed" but you can minimize the damage. Some stiffer crossmember and semi-trailing arm bushings like maybe polyurethane bushings would probably minimize the wheel hop on a ZX.

 

Jon

[Savage42]

Yep, it's a characteristic of the semi-trailing arm suspension in both the ZXs & 510s. I ran ZX rear arms on my 510 and made some modifications to the crossmember to make it fully adjustable for camber & toe, while raising the mounts up an 1". Here's a picture of the modified 510 crossmember (not too different than the ZX) w/ the ZX arms and Subaru (R160 LSD) diff.

 

http://datsun510.com/photopost/showphoto.php?photo=2144&papass=&sort=1

 

You can get a ton of 510 info at: http://www.dimequarterly.com In particular, go to the articles section. You may want to consider buying a back issue of Volume 2, Issue 3, which has a detailed write-up with drawings how to make your rear crossmember fully adjustable, which also allows you to run poly bushings and not have them die like they do with a slotted crossmember.

 

You can also check out some other 510, 'Cuda, & other pics in my personal albums at:

 

http://datsun510.com/photopost/showgallery.php?cat=500&ppuser=49&thumb=1

 

It's a great setup and something every serious ZX owner should consider.