ainlet manifold gasket and supercharger

Hi all. Just got my 97 Riv back from the shop after having the inlet manifold gaskets re-newed, new plugs and wires and a recon supercharher snout. All I can say Is WOW!!! what a difference feels and runs like a new car. Next job to do are the transmission mounts and then I will be happy for a while. For the recon supercharger snout see my previous post on reconditioned supercharger snouts. When I replaced the snout I had fitted a slightly smaller pully so now the SC kicks in real early and with a lot more oomph.
Len

Lenrapkins wrote:

Hi all. Just got my 97 Riv back from the shop after having the inlet manifold gaskets re-newed, new plugs and wires and a recon supercharher snout. All I can say Is WOW!!! what a difference feels and runs like a new car. Next job to do are the transmission mounts and then I will be happy for a while. For the recon supercharger snout see my previous post on reconditioned supercharger snouts. When I replaced the snout I had fitted a slightly smaller pully so now the SC kicks in real early and with a lot more oomph.
Len

...and if you did not retune the PCM, worse overall performance due to the PCM detuing the car while you are running to avoid detonation (this is called KR, "knock retard."). The SC does kick in earlier and you get more initial oopmh but the cost is still there. Others may chime in on this.

Albertj

What Albert says is true. Swapping to a smaller SC pulley is not a good idea unless you are able to, and have, scanned for Knock Retard first, and also after the swap to ensure your PCM isn't pulling timing due to KR. Many a SC 3800 owner has grenaded their engine by not modding properly. Not saying this is you, but... Have you scanned for KR?

1998 Riv wrote:

What Albert says is true. Swapping to a smaller SC pulley is not a good idea unless you are able to, and have, scanned for Knock Retard first, and also after the swap to ensure your PCM isn't pulling timing due to KR. Many a SC 3800 owner has grenaded their engine by not modding properly. Not saying this is you, but... Have you scanned for KR?

This isn't to whizz on your parade. Point is that for various reasons the PCM advances engine timing a lot depending on the sensor inputs. Without returning it, it will nto properly adjust for the increased air intake if you shrink the SC pulley.

So we figured we'd let you know this before you grenade your engine -- instead of letting you blow it up then smiling and shakign our heads.

Thanks to all for the input. Now I am very worried by the posts. Could someone explain to me what it all means in layman terms and what can I do and still keep the slifgtly smaller SC pulley. I was also contemplating a cold air intake to go with the SC mod., is this a bad idea also? At 69 years I am not a boy racer but I do appreciate performance in a car along with a good ride ( car I mean). Having driven high performance Jaguars all my life I was delighted to get my hands on this Riv and just wanted to pep it up a little. I really think it is the best car I have ever owned.
Len

Leonard, I think the answer depends on how much smaller is meant by "fitted a slightly smaller pulley". If you decreased the diameter by only 10% or less, there's little harm in it, although the engine's PCM will be trying to compensate for fueling issues you might run into under increased throttle. What the other guys have said are legit concerns, and the only way you can know for sure is to have the car scanned during WOT operation.

If you are dropping 15-20% or more, there could be a real concern if you operate at WOT on a regular basis. You may not hear anything wrong, and the car may feel quicker, but actually it won't be operating comfortably, and damage is a real possibility, especially in the colder months. Be very careful to use only premium gas, and use caution when flogging the car at higher RPMs. For normal A-B driving, you should be okay as long as you don't get the itch to race.

The fact that you haven't changed the intake or exhaust yet is a big plus, because you're able to enjoy the low RPM torque without much risk of moving too much air when the blower spools up. The OEM intake is protecting the engine by limiting boost, and ultimately horsepower. One area you want to be especially careful is cruising up steep grades in OD - if you hear anything strange, drop to 3rd gear while climbing the hills.

A few links for reading:

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/how-do-i-make-the-car-faster-t23.htm

https://rivperformance.editboard.com/series-ii-scans-tuning-pcm-f5/what-is-engine-knock-what-is-kr-t28.htm

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/smaller-sc-pulley-t3656.htm

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/why-is-engine-air-flow-important-t194.htm

Best of luck. Please ask if you have any questions.

AA nailed it... and again PLEASE ask if you have questions. Why not tell us the size of the new pulley? There are others who've made that mod that participate on this site, I'm sure they'll chime in and comment on what else they had to do to avoid excessive KR.

In the meantime I think you'll find the posts AA identified to be very good reading, and I think the reading of those posts will end your worry. Also, hint hint, take a look at the list of mods that AA has made, they are in his "signature' below all of his posts. The list will give you an idea of what goes into a Riv that will reliably do a 14 sec. 1/4 mile (and also still pass just about anything, including gas stations, on the interstate).
.
Albertj

The oem SC pulley is 3.8" diameter. I swapped to a 3.6 pulley with some supporting mods, but still found some significant knock retard, that's with just a 5% drop in pulley size. I've gone back to the stock pulley, and have found I still experience some knock retard on harder acceleration. Every engine is different, you'll need to scan for KR before you'll know how safely you may or may not be running with your smaller pulley. Please let us know what size it is.

I have just checked with Nate who reconditioned my snout. The new pulley size is 3.4" which is a 10% reduction. Nate races these cars professionally and has advised me that a 10% reduction will still keep the KR within 3 points of neutral or 0*. To be on the safe side however he says that a scan coud be re-assuring. He further advises a 180 Degree T-stat and a cooler spark plug. All of the above along with a good cold air intake should compliment the SC mod and give me the performance I want for day to day driving. I do not want to street race but getting away from the lights in front of the wanna be Mex racers is somewhat rewarding especially when they see an older man driving who is very young at heart. Thanks for all your posts and input. I feel that I know a lot more about my car now and also a little bit more tech savy.
Len

Good work, Len. I think we were all fearing the 3.25" pulley 'and-nothing-else' mod, which is a popular way to pop pistons. Your guy is correct in recommending the 180 t-stat and cooler plug. Most importantly, the scan must be performed at WOT to get an accurate result, and a trip through the mountains while scanning is a good idea if you intend to drive them.

Be careful adding a cold air intake - the extra cold air puts a demand on the PCM for more fuel, and it may not be able to keep up with a 3.4" without other mods. If/when you install the intake, another KR scan for insurance is a must.

I would also STRONGLY advise a 3" downpipe (about $140) before installing an intake with your set-up. See link:

https://rivperformance.editboard.com/t1142-hogan-downpipe

Len, did Nate tell you whether or not HE scanned your car for knock retard? While the 3.4 is a common swap on the street, it does have some risk, depending on your driving habits. As I stated, I had a few degrees of KR even with the OEM pulley. A 3.4 is not necessarily "safe". Drive carefully until you do the supporting mods mentioned.

Lenrapkins wrote:

I have just checked with Nate who reconditioned my snout. The new pulley size is 3.4" which is a 10% reduction. Nate races these cars professionally and has advised me that a 10% reduction will still keep the KR within 3 points of neutral or 0*. To be on the safe side however he says that a scan coud be re-assuring. He further advises a 180 Degree T-stat and a cooler spark plug. All of the above along with a good cold air intake should compliment the SC mod and give me the performance I want for day to day driving. I do not want to street race but getting away from the lights in front of the wanna be Mex racers is somewhat rewarding especially when they see an older man driving who is very young at heart. Thanks for all your posts and input. I feel that I know a lot more about my car now and also a little bit more tech savy.
Len

...along with the 180 tstat, might want to reprogram the PCM to turn on the fan(s) around that temp. Requires someone with the factory TechII tool, I think. Again, others will chime in on this. It may not be all that necessry or helpful if only because if you are moving the fans don't do all that much anyway, but it is something to deal especially because every engine is different.

As long as you are knocking around under there - while the car is idling after warmed up (say at a traffic light or when you have parked it and are getting ready to turn it off) look at the tach. If it is wavering even a little I suggest you consider pulling and cleaning the throttle body. Car wil show and run better if your idle is not hunting around.

Albertj