Best bang for buck?

[hey its me]

Hello all, I am still trying to grasp all the aspects of supercharging, so I am wondering what would be the next best move for adding some power. I have a 92 5.0 stang, all stock except an electric fan, ceramic shorty's and exhaust stuff, and then an sn92, which put a 4" blower pully on. The car has no tune, just the fmu, 24;b injectors, oh and an anderson powerpipe. The boost guage only reads 4 psi at full boost. I have no idea how much power it makes, and havent raced it YET, Im curious to see what it will run!

SO, im wondering if i should just buy a smaller pulley, or get the upgraded impellor shaft, or buy a basic chip for it ( The thing is, I dont know how an aftermarket ecu chip will effect it, or if its safe with S/C). Or should I man up and get a dyno+tune?

Thanks for any Help!

[DART340SC]

I would dyno it first to see where you are, that way from then on you will know what improvements you make and which direction you need to go.

[JPJP]

The Ø4.000 pulley is already a performance pulley. You could go smaller but gains may not be that noticeable. Keep an eye on the fluid as it will break down quickly. I am running a Ø3.750 pulley on my '86 Mustang.

I recommend the HO impeller next time you rebuild it. I noticed large gains using my "seat of the pants" dyno.

Bump as much timing as you can without pinging. When the ambient temperature is higher I just stay off the gas for everyday driving. I am running about 13-14° initial advance.

You are on a budget.....so I would recommend not doing much beyond that. A ported lower intake will also give you some flow. Good for about 10 HP is what I am told (which I too have done).

[Michael]

The boost seems a bit low @ 4psi. An SN with a stock impeller should see 5psi boost if everything is set up properly (ie. pulley sizing). I would size the pulley(ies) accordingly in order to get 5psi boost before doing anything else.

Once you get to 5psi boost, I would suggest a dyno+tune. A good shop should be able to help 'optimize' your setup.

And I would second JPJP's recommendation: an HO impeller is a very cost-effective way of upping the performance of the SN. Whether you do it now or during the next rebuild is entirely at your discretion.

Of course, not knowing your budget, it's hard to determine what you mean by best bang for the buck. If the "bucks" are there, then a VR4 kit is certainly another (viable) option. It brings the SN's performance right in line with some of today's 'modern' blowers, and gives you a lot of room to grow.

[hey its me]

wow thanks that is all good info. my budget isnt big enough for the VR4 yet, ( thats about $800 for kit and rebuild right?) Just doing a dyno doesnt seem like it would be very worth it if on a budget. i mean thats $500 for a dyno and tune.. which could maybe go towards the ported lower or gt40 lower. The thing is that i heard the air to fuel ratio would be lean if i added the intakes wouldnt it?
Good tip on timing, i just didnt know how much advance would be safe before "knock" ( i think is what its called.) And i think I would just wait until i need a rebuild to do a VR4. but for the mean time the HO impellor seems like a good choice. I just have no idea how much the impellor costs and how much it would cost to have that put in. can anyone help with some advice?

Thank you for all the help, im new to this, and im just trying to learn as much as possible

[Michael]

Never underestimate the value of a proper dyno+tune. If you're concerned that the engine isn't running at it's optimum, throwing more parts at it (ie. ported intake, HO impeller, etc...) isn't going to make things better.

The H.O. impeller for the SN isn't too expensive to purchase outright. It's about $150 or so. But I don't know how much the install will be. If you send the head unit to Paradise Wheels or CUNDN Racing (the only places I know of that sell the H.O. impeller) to install the new impeller they will more than likely insist on some kind of rebuild for the unit as they will be opening it up to install the impeller anyway. The rebuild may be as simple as new seals, but if they find anything that's worn (ie. bearing races, drive balls, etc...) then those parts will be replaced as well, which will obviously increase the install price; a VR4 kit may not be that much more when you look at it that way.

IMHO, the H.O. impeller really becomes a worthwhile upgrade if you do the install yourself. That way you can inspect the blower's internals and replace what's necessary yourself. Of course, that's highly dependent on how comfortable you feel about opening up one of these units. They aren't complicated, but the intimidation is certainly understandable.

[hey its me]

yea i agree. The car runs smooth and great, i feel like it has quite bit of power for 4 lbs of boost on a stock engine. Yea if rebuild in necesary i think the vr4 would be a good choice. But then if i do that, i would have to get a dyno tune. +500 bucks, then probably a bigger fuel pump + injectors. so if i can get by with throwing the intake in, along with the HO impellor without a tune that might be the way to go. I just dont know how that wil effect A/F ratio.

I would like to take it apart myself, but i dont know what kind of tools i would need to get, cuz i know shimming it right is important. ( unless its just a direct replacement).

[JPJP]

The VR4 may provide too much boost for the head gaskets.

I don't think the ported intake will cause it to run lean. It will just improve airflow.

[Michael]

I don't think the ported intake will cause it to run lean. It will just improve airflow.

I agree. An intake swap will have very little effect on A/F ratio. It will only serve as an improvement to overall airflow by providing less resistance to what's already coming in.

I would like to take it apart myself, but i dont know what kind of tools i would need to get, cuz i know shimming it right is important. ( unless its just a direct replacement).

The H.O. impeller install (from what I can recall) is a relatively simple remove and replace. If you perform a search on the forum here, you should find a few posts with photos showing the SN's "internals" and what it takes to open one up. There are no special tools required (other than maybe a good torque wrench).

[hey its me]

[quote=Michael;63737]I agree. An intake swap will have very little effect on A/F ratio. It will only serve as an improvement to overall airflow by providing less resistance to what's already coming in.


Thats good news! the part is dirt cheap too. Yea I have some researching before I feel comfortable pulling the unit apart, if i get the impellor. How muh of a difference does it make?

[slownlow]

All good points...But I have to say it.You wanna play then its gonna cost ya..If its running good and you want to drive it?Just run it as is...:) Spend your money on gas:)

[Michael]

Thats good news! the part is dirt cheap too. Yea I have some researching before I feel comfortable pulling the unit apart, if i get the impellor. How muh of a difference does it make?

The H.O. impeller is good for a 1psi - 1.5psi increase in boost (approximately). On an SN producing 5psi with the stock impeller, the H.O. impeller should produce between 6psi to 6.5psi. May not sound like much, but for the cost it's a nice, noticeable increase in performance.

Unfortunately, I can't comment one how much "power difference" the impeller upgrade will make, since that will heavily depend on how much power your engine is producing prior to the upgrade.

[444]

The H.O. impeller install (from what I can recall) is a relatively simple remove and replace. If you perform a search on the forum here, you should find a few posts with photos showing the SN's "internals" and what it takes to open one up. There are no special tools required (other than maybe a good torque wrench).

I would caution that any time you swap an impellor for a different unit, you may need to reshim it. The shim kit is 20 bucks, then all you need is a cheap set of feeler gauges.

[JPJP]

Depth mic. works better. I was unable to get my feeler gauges in there.

[hey its me]

You have all been reallly helpful thank you. I agree I should get 5 psi out of it first. Speedystang said that I dont have enough ball tension on the units. (It is easy to turn by hand wih the belt off, and it should be hard to turn by hand).

Does anyone know how to fix this problem?

Thanks