Finally Installed the PI intake - review of my mods to date

bhuff30

Founding Member
Dec 11, 2001
6,037
35
129
Olathe KS
Several months ago, I found a PI intake for cheap. I finally got around to installing it and I'm very happy with the result. It feels like a completely different engine above 4000 now.
The intake was from a police interceptor and had a foam glove around it to protect it from heat. I kept that piece and installed it too. The install was pretty simple and the PI intake literally slid into place easier than the NPI intake came out.

The power gain with the PI intake is very noticible. I already had PI cams and an offroad H pipe, so the NPI intake was really holding the car back. I found myself actually hitting the rev limiter today, which is only 5700. I had never hit the rev limiter before because there was no reason to rev it that high before. Here is a my review of the modifications I've done to date:

Stock: Torque dropped off starting at 3800 and it was pretty much done making power by 4500, but I reved it to 4800 at the track. It ran 14.6 in the 1/4 with a poor 2.3 60' time.

O/R H pipe: Definitely added torque all around and gave a bit more power on the top end. I felt a 5100-5200 to be a good shift point and ran 14.2 in the 1/4.

Drop in K&N: No noticible change in power, but I don't have to replace paper filters now.

Underdrive pullies: if I rev it high enough (and out of the power band), I could feel a slight difference. They were free, so why not.

PI cams: these were a huge PITA to install, but I pulled the front cover to replace the guides while I was in there. They gave a little more top end again. I felt like 5500 was a good shift point, but the power gain was very subtle and quite high in the rev range, without much additional torque.

Tweecer: I added 4* of timing and lean out the top end quite a bit. It just made a bit more torque all around, but a pretty subtle gain

PI intake: I bet a 5800 shift point would be good, but the rev limiter is getting in my way at 5700. The car pulls much harder above 4000. This by far the biggest power gain, but it was the last major restriction too. I can understand why everyone says gears, gears gears now. In stock form, the 3.27 gears were a nice match for the power band which ended at 4500. Now, some gears would really help to keep the engine in the newly formed power band from 4000-5700.

Pretty soon, I'll put the tweecer back on this car (it is on the 88 at the moment) and see how it feels. I'll fine tune the AFs, add the timing back in, and raise the rev limiter a bit. I really need to get it to the track to set a new time though. That's a lot of changes since I ran 14.2. ;)
 
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I couldn't agree more with your findings Brian. I too replaced the intake and cams separately, although I replaced the intake first.

The PI intake w/ the NPI cams made a big difference and increased the shift point by about 500 RPM's.

Later when I replaced the NPI cams with the PI cams, I really didn't notice that much of a difference, although the exhaust at idle was much deeper and had more of a rump to it. :shrug:

I didn't pull the front cover, I just removed the cam covers and had my brother hold the timing gears with a vice-grips while I swapped cams. If I had to do it all over again I don't know that I'd have bought the PI cams.

For the work involved in swapping cams, I really wish I would have bought a pair of MHS stage 2 N/A NPI cams. I'd like to buy them now, but modding is put on hold when you have a kid and I have another one on the way. Maybe I can get them in the spring :D
 
Where you getting that 5700 RPM rev limit from? Should be more like 6100. The needle can lag behind a good bit when it's sweeping across the dial quickly though so maybe it just looks like it's that low or is was it changes in your tune for some reason? Before PI cams/intake it feels like a rev limiter right around there though :nonono:

Anyway, congrats on the intake - remarkable what a difference the cams & intake make to the top end, isn't it?

Your list of mods and subjective experiences is pretty similar to mine:

I wouldn't bother with U/D pulleys if I were starting over but they were either super cheap or free.

I noticed about 500 extra usable RPMs with the PI cams (did those before the intake). PI cams are definitely worth it if you're not paying someone to do the labor.

I noticed more seat-of-the-pants power across the board when I bumped up the timing a few degrees, but especially in the low, daily-driving RPMs along with snappier throttle response down there

The O/R H-pipe felt like it added power in the mid and upper RPMs but also made things feel a little soggy at low RPMs - sorta canceled out the snappiness from the extra ignition timing. Also made the exhaust louder. A LOT LOUDER! :D

The PI intake added another 500 RPM to the usable RPM range and now it's not completely pointless to run it out to 6K RPM. Totally changed the character of the engine above 4500 RPM, feels like a high-performance engine and not an undersized truck motor.

Still idles like stock, but with the slightest hint of lope and is perfectly happy puttering around back & forth to work between 1200~2000 RPMs.
 
:lol: yep the factory NPI stuff is laughable. I remember before I had installed the PI intake and cams, the power curve would just face plant at 5K rpm's. I actually wound it out to 6 grand a few times with the NPI stuff, it sure made a lot of noise but didn't really go anywhere, lol.
 
I have a TwEECer, so I checked the rev limiter in the code. There are 2 rev limits listed, I assume one for neutral and one for in gear. One is on at 5700 and off at 5500 and that's the one I found in gear I believe. The other is on at 6050 and off at 6000, which I believe to be in neutral. If I stupidly rev it in neutral, I get to that rev limiter. However, you are very correct to ask about the accuracy of the tach. They can often be up to 500rpm off, but mine seems to be within 100rpm.

Like I said, before doing the PI intake, I had never touched the rev limiter. I think it would take a lot of effort.

Where you getting that 5700 RPM rev limit from? Should be more like 6100. The needle can lag behind a good bit when it's sweeping across the dial quickly though so maybe it just looks like it's that low or is was it changes in your tune for some reason? Before PI cams/intake it feels like a rev limiter right around there though :nonono: