A few questions

Kyler

Registered User
Hey, I have a few questions for someone here who knows alot more then me about what their talking about.

1.) I have an SCP 3" intake, I want a larger throttle body but when changing to a 70, 75, or 85mm, which is recommended and do all sizes require a new or ported inlet plenum?

2.) What are the stock Injector and spark plug sizes in my 90' XR7, and what are recommended as far as newer ones?

3.) Gears? My friends tell me 3.73's but when I look around people with 5 spds, (my car) get 3.27's or 3.55's, so what ones should I get?, Where from?, How much?

4.) As far as mods, I mean I've done intake/exhaust already, but what would be the smartest thing to go for next?

Thanks, :confused:
 
1. 75mm is the biggest you want to use on a stock plenum and requires port matching. You won't fit the 3" intake on anything larger than 75mm and it may be a tight fit for your coupler on a 75mm. Depending on mods and what you plan to do the throttle body might slow you down until you get more air flowing into the engine by making the supercharger more efficient and overdriving it.

2. Stock injectors are 30 lb/hr. injectors. Your stock fuel pump is something like 110 lph and its not nearly enough. I've seen stock SC's lean out near redline. I will recommend a 190 lph or 255 lph pump but the stock injectors are ok for you for the time being. Plugs are AWSF34pp's and if you want put some AWSF32pp's (pp for double platinum) that will step down a heat range and will be ready if you want to run nitrous (but not on a stock fuel pump you don't!) If you cross reference the plug numbers you can go with autolite double platinums for about half the price of the motorcraft plugs and they are identical. Stay away from Bosch Platinums as they suck in forced induction cars.

3. I have 3.27's in my 5-speed. It really made the car feel fast. I was contemplating 3.55's but since I do a lot of highway driving I felt 3.27 was the best for mileage and acceleration. Plus w/ 3.55's you are close if not in 4th gear going through the traps at the 1/4 mile. 3.27's will put you right up close to 4th. I've had to shift to 4th before at the track. But I had smaller tires so it alterred my gear ratio more. Gears are one of the best mods you can feel a difference by doing. I say 3.27's. 3.73's are for mustangs but we have a different transmission and they have different internal gear ratio's. They have a T5 we have an M5R2 mazda truck transmission. Ours is stronger!

4. Next up I'd do gears, and a blower pulley. Then a raised blower top, and a double intercooler. You will want to upgrade your fuel pump soon so it could take priority but you won't feel any faster from it.
 
Kyler said:
Hey, I have a few questions for someone here who knows alot more then me about what their talking about.

1.) I have an SCP 3" intake, I want a larger throttle body but when changing to a 70, 75, or 85mm, which is recommended and do all sizes require a new or ported inlet plenum?

2.) What are the stock Injector and spark plug sizes in my 90' XR7, and what are recommended as far as newer ones?

3.) Gears? My friends tell me 3.73's but when I look around people with 5 spds, (my car) get 3.27's or 3.55's, so what ones should I get?, Where from?, How much?

4.) As far as mods, I mean I've done intake/exhaust already, but what would be the smartest thing to go for next?

Thanks, :confused:

If you get a 70mm, you can port the inlet if you want. If you get a 75mm, then I would highly recommend porting the inlet. If you get the 85mm, then I would consider getting a Magnum Powers Inlet Plenum.

Like Scott said, you've got 30# injectors. A local SC'er dyno'ed this weekend making almost 250 RWHP (248 if I remember right?) and still has stock 30# injectors. What size to get when you upgrade? Depends on your final power goals.

If you decide to go with 3.27's, you can probably find a complete rear end fairly cheap since most auto SC's have 3.27's and I'm willing to bet that you can just swap them over with the right speedo gear. I think 3.73's might be a bit much for the 5spd. If you want more zip than the 3.27, then go with 3.55's.

Next mods (going with Scott again) Upgrade fuel pump - I would do a 255lph pump. Followed by a double IC and maybe an OD pulley for the blower.
 
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