vibration

[jmwilso2]

I did some playing around with it today. With the truck in neutral there is no vibration regardless of rpm and programmer level. When driving though there is only normal intake noise with the gryphon set to stock and a slightly louder with it set to tranny only, but in 87 tow it howls whenever there is load on the engine. Cruising along there is no abnormal noise but if you accelerate or even go up a small hill with the cruise control on it makes enough noise that you have to raise your voice to talk. Im still not sure if it is coming from the intake though i think it must be because the noise was very subtle until I installed the cai.

[Jackpine]

Now you're describing "intake drone". Bill can adjust the tune to minimize this or even eliminate it, but it WILL require an adjustment (new tune). A simpler solution is to install the DIY Gotts Mod intake which has NO drone and requires no special tuning, and it also give you an increase in power.

The earlier vibration problem could be something known as "tranny shudder" which used to be an issue a couple of years ago. I think Bill can make minor adjustments in your present tune to get rid of this.

- Jack

[jmwilso2]

Hi Jack, I'm still running the canned tunes I wanted to make sure all my bolt on mods were going to be staying before I get the customs written. If it is just intake drone why would it go away when set to stock or tranny only. I am seriously considering the gotts mod I would definitely do it if I had the chance to do it over again. I might call S&B to see if they'll take back the intake. I'm just having a hard time understanding why it only does it when there is load on the engine and set to 87 tow but under no other circumstances. Your idea that my first issue and the air intake issue are completely seperate sounds pretty likely to me now that I am thinking about it more. I am relatively certain that the vibration prior to the cai install was coming from around my feet and after the install it is higher up in the engine bay. I am also relatively confident that the loud noise after the cai install cannot be tranny because anything that loud coming out of there would have to affect drivability. So that leaves the question as to whether the original vibration was coming from the factory intake and is being amplified by the cai or if they are indeed seperate issues.

Thank you for the input I really appreciate any advice I can get about these things.

Joe

[jmwilso2]

Ok Ive reached a decision. I'm going to return the S&B and do a Gotts mod if it doesnt measure up (but I think it probably will from all I've read about it) I'll try to find an airforce1 intake.

Joe

[Jackpine]

As far as I know, the canned Lvl 2 and 3 tunes modify fueling, timing and probably other parameters that effect how air is moved through the intake.

Because air is moved through the intake in discrete "pulses", each time an intake valve opens, there are pressure waves created that can reinforce each other at certain frequencies and these create the "drone". The helmholtz resonators on the stock intake are designed to cancel these out, even when they occur on a "tuned" engine.

The commercial CAIs were also designed for stock tunes. Anything that modifies the intake timing, is outside their design parameters. When Bill adjusts the tune to get rid of intake drone, it's my understanding that he sets the intake timing back to stock.

All of these conflicting requirements have the effect of reducing the benefit of a commercial CAI.

Since the Gotts mod retains the stock design, while removing the "bottleneck" at the snorkel you don't get the adverse effects.

- Jack

[jmwilso2]

Thanks Jack that does clear it up quite a bit for me. I should have thought of that but it just never occured to me that air induction does occur in discrete pulses same as exhaust. It makes perfect sense though. I just finished installing the Gotts, I did it the same as yours. I test drove it and it seems to drive about the same as the S&B and I have a longer trip to go on
tomorow so I'll find out if I'm still getting the better fuel ecomomy the S&B was giving me. If I'm not, I think I'll try to reach up inside the intake tube and plug or tape over the holes the lead into the silencer. I might do this anyway to see if its safe to remove it without getting that droning noise back. The darn thing does look pretty stupid. If all else fails I may just buy the airforce 1 intake but its so expensive I find it hard to justify the cost from a return on investment standpoint. It would be a "because its cool" purchase as opposed to the easier kind where justify it to myself as saving money in the long run.

Thanks for all the advice.

Joe

[Jackpine]

I would NOT remove the resonators. If you look at the design, they do not let hot air in, but, they act kind of like spring/shock absorbers, with the holes into the chambers and then the holes in the bottom of the chambers.

It's a bit like a tuned port in a bass reflex sound system loudspeaker. The enclosed space is the spring and the port allows a damping action like a shock absorber. If you tape up the holes or cut the chambers off, you are pretty much back to your commercial CAI design.

- Jack