Has anyone had perf. problems when using SLPs siamese intake runners? I have a 92 350 Z with a Paxton SC. Last year I was able to run 12.7 @ 108 mph with 1.7 60 ft times. This year after installing the runners I can't get below a 13.3 @ 105 mph with a 2.0 60 ft time. I had the same problem when I ran NA but I also had a bad spark plug wire. I'm going to check the ign. system but am looking for any similar stories before I switch back to the factory runners. Thanks in advance.

 

I had the SLP runners and didn't have a problem.

 

No problems here either. Are they as they came from SLP or have you ported them out?

 

They're as they came from SLP. I'll start checking other things. Did you guys notice any decrease in low end torque and better high end? Or was it a good improvement through the entire RPM range. Thanks again.

 

Mine were a fine improvement all through the rev range. Shifting at 5500 was what made the car quicker also instead of 5000. This was on a 350 engine, auto trans 3.73 geared combo. I did port my plenum in the process also, then I matched all of the gasket surfaces with a die grinder. Goodluck, maybe you did something wrong on install but i'm sure you already checked everything.

 

My stock IROC shifts at 5500 rpms. Is it supposed to shift at 5000? Just curious, my old LG4 used to shift at 4500, and I got scared the first time I floored the iroc, as I was waiting for it to shift...... and it held to 5500

Will

 

Stick the car on a dyno n look at peak horsepower, most TPI cars will peak around 4400rpm like mine - I have my shift points at 4600rpm, I no longer have that stupid "lag" waiting for the car to shift before it starts pulling again. Revving higher is only beneficial if your horsepower peaks that high, most people don't, never seen a stock TPI peak anywhere in the 5000's before. If you find yourself waiting for it to shift, and the car suddenly jolts n starts pulling again when it gets into 2nd gear, it means you went past your power band, one way to test your power band, and I don't really reccomend this.... find a big long empty stretch of road n see how fast you can go in 3rd gear - the RPM where your accellaration dramatically slows down is the RPM where you're losing power - you may be able to get to 125mph, but usually you get to around 110 quick, then need to wait forever for it to get over 120 - so the RPM you were at when you were doing 110 is probably close to your peak power. Again, don't go blaming me if u kill yourself or get yourself arrested, but it is effective.

 

Nitro,
700-R4 wise...Would you agree that shifting higher on the 1-2 shift is beneficial? Mainly because of the well know "drop in rpm" since the gear ratios are spead so far apart...To a point I found that over revving 1st gear DEFINATELY helped acceleration in second gear only because the car was in the correct rpm range once second was engaged. Then I could reall tell that over revving the 2-3 shift was pointless because there was a lot of wasted time getting to 5500 instead of the normal 5000. later fellas!

 

I agree with Autoroc, but my car shifts at 5500, and right into second, hard..... There is no lag and it pulls big time going into second.... But I think I remember the original owner saying something about a mild shift improver being used in the rebuild.

WILL

 

Well I think the SLP runners are set up to help the TPI's problem with no high end torque. So I would imagine that they made it so that you get more power up high but sacrificing some of the low end grunt. I think it may just be a problem with your particular set-up. Because obviously you had the car set-up well with the stock TPI. So I would think that it would just be a matter of tuning to the adjusted RPM band that the new runners offer.

 

I havent played around with that, I find that shifting 200rpm past peak hp gives me the smoothest driving flow, I can't stand the lag feeling between shifts, one reason I hate driving and being a passenger in a 5-speed car, unless its being competition shifted on every shift, it'll **** me off having the car pause everytime u change gear then start pulling again.

 

Well, it could be a lot of things. Start off by upgrading or checking the ignition system. What are you plugs gapped at? Try .035 or .032 you may blowing the spark out with the blower. Try upgraging the coil. Those new runners are going to flow better than the old ones. That's why you bough them. With more air means more fuel. Try and adjust fuel preesure. Hope this helps. If all else fails hook it up to scanning tool so you can see what's going on with the motor.

 

Thanks for the replies. I scanned the engine and the O2 seemed flat, it only ran .700 mv at WOT and did not toggle at idle with the CTS at 212 F. I know the toggling isn't an issue at WOT but the .700 seems low as I used to run .900 mv WOT through the entire RPM range w/8lbs of boost. I gapped the plugs .010" lower than spec. which is I think .045" so they should be at .035". I'm going to try a tune up first and then maybe an O2 if it doesn't start acting right. My MAP is steady at an idle and I don't hear any popping through the exhaust so the rockers should be adjusted correctly (1/2 - 3/4 turn @ 0 lash). I forgot to mention I also installed 1.6 roller rockers. My injectors were already upgraded to 30 lb.hr. before this. I was mainly looking for some comparable info. on people that have used the SLP runners. I do have an adj. regulator so I can bump up the pressure if needed. Thanks again!