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 Post subject: More HP for Z31
PostPosted: Wed Feb 03, 2016 3:33 pm 
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Joined: Fri Dec 25, 2015 7:39 pm
Posts: 697
Location: Long Island, N.Y.
Would I gain ANY horsepower for my 1985Z n/a if I tweaked the timing a degree or two and/or increased the size of the throttle body? Or would I just use more gas and develop a possible pinging? I'm just shooting in the dark looking to make it even better. I think I know the answer I'm going to get from the Engine Guru's, but I just had to ask the members. Take it eaZy on me please. :)

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1985 300ZX- GLL Dark Pewter Metallic - Survivor


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 Post subject: Re: More HP for Z31
PostPosted: Thu Feb 04, 2016 1:14 pm 
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Joined: Wed Feb 29, 2012 11:44 am
Posts: 588
Location: New Haven, CT
Hey Howard,

I think you can gain just a few HP from tweaking timing but not anything substantial. A larger TB will improve response but is unlikely to net you any HP as the intake plenum is the major flow restriction on the VG30E.

If you haven't already, swapping to a cone air filter will net you more HP than timing or TB. If you are still interested in changing the throttle body, the Stanza 55mm one is known to work well--though you will need to port the intake manifold to match in order to really make a difference.

What's on the car currently?

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Justin
1986 Z31 NA 2+0


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 Post subject: Re: More HP for Z31
PostPosted: Thu Feb 04, 2016 7:07 pm 
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Joined: Fri Dec 25, 2015 7:39 pm
Posts: 697
Location: Long Island, N.Y.
Can a K&N type of cone filter actually allow any REAL hp gain? They usually just make it SOUND somewhat more throatier. My 1985ZX GLL n/a is 100% bone stock with 32,000 original miles. Everything looks, works and performs like it did the day it rolled off the dealers lot with all it's original parts. So when you ask "What's on the car now?" I don't know how to answer you because I'm not much of a motor head. Just a hands on home mechanic. Plugs, points, wires, timing, carb swaps,water pumps, belts, alternators, tires, brakes, etc. :?

I'm aware "more air + more fuel + low restriction exhaust" = vroomZ :D

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 Post subject: Re: More HP for Z31
PostPosted: Fri Feb 05, 2016 11:29 am 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 14779
Location: CT
TRUE, but the real money today is in bone-stock classic Zs and ZXs. People pay more for Z carz which are unmolested time-capsules, unchanged from the original. So while you might gain a horse or two by modifying your engine, you would devalue your car on the classic market by doing so.
I think the logic behind that goes like this: If you modify your car the way you want it, I might want your car but wouldn't have modified it that way. Knowing I would have to reverse your custom work in order to make the car the way I want it, I would offer you less money for your car than if it was stock. ALSO, if I intended to enter the car in any show, your modifications would make the car less desirable, so I would be less likely to earn any recognition for it.

And a V6 with less than 35K miles on it is only *just* broken-in!!!

What you do with your car is not my business, but MANNN......if I owned an original Z with only 32,000 miles on it, I would be VERY careful not to modify a single item on it! Your car is worth FAR more in its original state (especially with low miles) than it will ever be after you modify it. These cars are climbing in value each year, until you modify them.

Just my 2 cents. Sorry. :oops:

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 Post subject: Re: More HP for Z31
PostPosted: Fri Feb 05, 2016 4:49 pm 
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Posts: 697
Location: Long Island, N.Y.
Hi Frank. I'm SORRY if I scared you. There's no way I would do anything to my baby that would "deform" her. If you read the thread carefully you would realize that I was just asking opinions of members about tweaking the timing and/or possibly changing the throttle body to one that might deliver more fuel (more hp?). I don't even know if there is a higher volume bolt on that I could use. Maybe the turbo had a high output throttle body? But I wouldn't be willing to change the stock exhaust, so that probably wouldn't produce any usable HP. Right? I was just throwing out some things that I used to do to some of my cars fifty years ago that gave me a slight edge when I ran at National Speedway out on Long Island.
I guess old school tricks don't necessarily transfer to these computer assisted cars. I'm learning. It just takes the old folks a little longer for it to absorb. Maybe a little nitro? Kidding Frank. This car STAYS 100% ORIGINAL for as long as I'm alive. Promise.

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 Post subject: Re: More HP for Z31
PostPosted: Fri Feb 05, 2016 6:47 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
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Location: CT
:lol: :thumbs_up:
Whew! You had me scared there for a moment. :lol:
Justin knows a doZen ways to squeZe more ponies out of his ZX (he's our motosports Guru). His car has won trophies on the AutoCross track AND in our annual car show. But he's probably got more money invested under his hood and in racing tires than I have in my entire car.
His car looks great, but we only get to zee it from behind.

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 Post subject: Re: More HP for Z31
PostPosted: Fri Feb 05, 2016 9:52 pm 
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Joined: Fri Dec 25, 2015 7:39 pm
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Location: Long Island, N.Y.
:lol: :thumbs_up:

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 Post subject: Re: More HP for Z31
PostPosted: Wed Feb 10, 2016 1:35 pm 
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Location: New Haven, CT
Haha, thanks Frank! I am by no means any authority on how to make HP, but I have tinkered here and there to see what low-hanging fruit I can get.

The throttle body doesn't deliver fuel--only air. The fuel delivery system is via your injectors. And generally you don't want to touch that in a lightly modified or stock non-turbo car.

That being said, more air flow on the intake end will net you 5-10 whp. This has been tested. The owner of the site http://www.az-zbum.com/ has dyno runs on a bone stock z31 NA with various cone filters versus the stock box. I guess the site is being redesigned at the moment because I can't bring them up. I can only get this tiny google cache image up (sorry!). It is hard to see, but the black curve is with the factory air box. You can see that the horsepower curve shows small gains all across the board that leads up to a pretty significant increase at peak horsepower when using a cone filter over the oem air box. However, the big kicker are the torque gains that are significant from low RPM up to the peak torque.

Anyhow, I find that the cone filter helps more for throttle response and the power is a little bonus. I still have my factory air box and can go back to stock if I choose (easily reversible mod).


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1986 Z31 NA 2+0
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 Post subject: Re: More HP for Z31
PostPosted: Wed Feb 10, 2016 11:34 pm 
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Location: CT
Justin, I thought you ran a pop charger on your car a year or so ago? Did you actually feel any difference with that?

Thinking about increased TB size makes me picture lower air velocities in the plenum. The engine is simply a big air pump, and it has a 3L capacity for air. If you make the air enter the engine thru a small hole (TB) you get high airspeed and high vacuum. If you let the air enter thru a larger hole, the airspeed will be slower and the vacuum will be lower, too. Would anything suffer if you did that? If you gave your car a larger throttle body, wouldn't you have to make it a deeper-breather by installing lumpier cams in it?

When we were kids we replaced the original 2-Bbl carb and manifold on my buddy's 265V8 chevy, and put on big triple Stomberg single-barrels. The car bogged sadly because opening all that intake area just dropped the manifold vacuum, which lowered the airspeed thru each venturi and actually messed up the fuel delivery. None of the vacuum-operated accessories worked well, either (including the power brakes). Had we put a bigger cam in the car we might have made use of the added carburetor area and his '55 chevy might have been the screamer we all hoped it would be. We reversed our work the following weekend and were far happier with the stock performance.

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 Post subject: Re: More HP for Z31
PostPosted: Thu Apr 21, 2016 12:35 am 
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Joined: Sun Apr 01, 2012 4:19 pm
Posts: 1644
If you are seeking cheap, easily reversible to stock power, the KN Intake is the way to go. Personally for me, when things felt like they were slowing down at 4K, installing the intake really made a difference. Exhaust made an even bigger difference. But I don't blame you on keeping that beauty stock. I personally don't do anything I can't undo to a stock condition. Not because I care about resale, but because if I get old (not when, but *IF*) I may not like what I currently like at 23. Just my .02. Who cares what Johnny Appleseed thinks my car is worth in 50 years.

Check out my posts on the intake I installed here:
viewtopic.php?f=3&t=7356&start=150


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 Post subject: Re: More HP for Z31
PostPosted: Fri Apr 22, 2016 8:35 am 
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Joined: Fri Dec 25, 2015 7:39 pm
Posts: 697
Location: Long Island, N.Y.
Thanks. :thumbs_up:

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