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Ztherapy SU's, wow what a difference


zguitar71

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I just go my Ztherapy SU's in the mail yesterday and put them in today. It only took about 1.5 hours to get them in and tuned. I watched the video last night which was a big help. I took the car out and it feels like a hole new motor. The motor now pulls to 6500K+ or so where as before it started to loose power at 5500 or so. The power through out the power band has increased noticably. The old SU's must have been in bad shape. I hit 2nd and the car spun the tires and launched forward like never befor, usually the tires barely spin, just a chirp. It feels like I gained 25HP, that could be more than reality but it feels great. The idel is much smoother and it sits right around 850. I'v allways assumed the car had a stock E31 cam in it but it sure pulls hard higher in the revs now like mabey a stage 2 or something or mabey it is the SM needles; I just do not know. The idel has allways been a little lumpy, I just though it was the carbs and the stae of tune, mabey it is a bigger cam. I am happy with the carbs though. Now I get to see how they do on the autox course. The old ones cut out around every right hand corner. If these don't do that then I will be so happy.

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Yeah SU's are great carbs I didn't know how good they were till i went in a mates 3.1ltr L28 just running SU's one of the few cars I've been in that throws you back into your seat on take off.

That's why I'll never understand the single carbie change over.

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Chris,

How would this work as a change in the ZTherapy owners manual......? "If after installing your ZTherapy carbs the engine continues to cut-out on right hand turns while autocrossing...... Run only autocrosses with left hands turns." I will put this before the board. Nyuck nyuck

When the snow finally melts and you get a chance to run, let us know how the right turn problem is..............

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Chris,

How would this work as a change in the ZTherapy owners manual......? "If after installing your ZTherapy carbs the engine continues to cut-out on right hand turns while autocrossing...... Run only autocrosses with left hands turns." I will put this before the board. Nyuck nyuck

When the snow finally melts and you get a chance to run, let us know how the right turn problem is..............

Sounds good to me. I will let you know how they work on the next race which is the 31st of this month.

Chickenwafer, I had 4 bolt SU's originally so that is what I got from Ztherapy. I believe if you have 3 bolts for cores then you will get 3 bolt SU's from them unless you work something out with them. I'm sure bruce knows the answer better than I. The carbs are modified a little, they incorperate roller bearings and other innovations that the originals did not have. They reengineer them onto a better more reliable carb. They are not ported or anything like that though. I highly recomend them. I had the option to go with a Mikuni tripple set up (used) for nearly the same price, I am so glad I went with the Ztherapy instead, baisically they are like having brand new carbs.

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Yesterday I got a call from a Z friend asking if I wanted to goto Helena MT for an autox. Helena just happens to have the best autox area I have ever seen, it is a 6 acre lot with a 1.3 mile road course attached to it. It is used for the Highwy patrol as a training ground, all the pavement is in great shape and it is glass smoothe. So I went today and raced and the SU's performed perfectly. NO MORE CUTTING OUT AROUND RIGHT HAND CORNERS, LIFE IS GETTING BETTER ALL THE TIME. I had originally told my friend I could not go due to my diff bearings being so bad, so he said if I pulled his 3.9 R190 with LSD from another race car that was wrecked I could use it as long as I like. So yesterday I pulled the diff, yanked my r200 4.38 and put in the R190. Much better gearing for my car and motor and the clutch packs are in better shape too, it really hooks up. So in the last 4 days I went from a Z with horrible carbs and a noisy, too low, oversized (R200) diff to a Z with new killer SU's and a Nismo R190 diff with the right gearing. The change has been drastic and all for the better. My friend used to race my car on occasion before I bought it from one of his friends. I let him drive the car and he could not believe the power difference. He has a 3.1 stroker with 12.5:1 commpression that runs on 112 occtane and races in Emod. His car is fast probably around 300 HP. I can keep up with him through 1 and 2 then he starts to pull away in 3rd. So I am getting the same 0-60 times as his car but in the 1/4 he would kill me, that is where the strokers shine. Befor the Ztherapy SU's I could not even dream of staying with him to 60. I really think the old SU's were masking what the motor had in it. I am making power to nearly 7K, before it stoped at 5700. I used to think the E31 head was stock now I think it must have bigger valves and a larger cam and possibly some porting.

So life is good and I recomend Ztherapy SU's to anyone considering triples or having troubles with there present SU's. Oh yea the service was great too!

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Just wondering... on average, how much power do the ZT su's give on an L28? mpg? and what would u guys prefer between triple webers and ztherapy's?

i own a set of triple webers but the mpg is horrendous and i was thinking whether or not i should get SU's.

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I went to Helena raced and came back. I drove 80-85 most of the way and had some small runs too 105-110 with my Z buddy over the pass between here and Helena plus the racing and I averaged 23 MPG. Not bad for the amount of lead footing I did. I have an 83 5 speed and a 3.9 diff. In town with out driving like a jack a$$ I get around 21 and on the road under the same driving conditions at a steady 75 I get 28-30.

My friends Z is stroked (3.1) and has tripples with 12.5:1 compression and I can stay with him to 60. After that I get left behind but I think that is not bad for a L28/E31 combo with stock SU's. I might be wrong but I think I am making about 225 HP at the fly wheel. With the right tweeking and money in your pocket I bet you could get 250 HP at the flywheel with SU's on an L28. I definatly will stay with SU's. I do not think you can install tripples and set them up in 1.5 hours, or at least I know I can't. I think both are easy to keep in tune once they are set up but the set up time is less for SU's. Tripples have there place but for street cars and cars thet stay below 7k I think Su's are fine.

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  • 2 weeks later...

Having personally seen a few cars running ZT SU's (including Steve's white 240), and the carbs themselves in various states of assembly, I can vouch for their effect and overall improvement on stock SU's.

Lots of little details are taken into account, for example on those I've seen even the throttle butterfly screws are flush to improve CFM. Probably not noticeable by more than a dyno or an all-race engine, but nice to know its there.

Perhaps someday I can afford a set. :)

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