Hogan Downpipe

No "pinging" from mine either. It ticked for a little while after it was installed, then stopped doing it forever.

1998 Riv wrote:

I'm not wrapped and have no issue with such a noise from my Hogan DP.

That's good to know (though I think Ben mentioned it to me b4.)
I wouldn't think that header wrap would help the downpipe flex-joint if it did make noise, because the flexing would probably break or loosen the wrap... Headers themselves don't have that motion.

As far as the joints on the Hogan site, if you start at the main page and go to accessories instead of straight to downpipes, there is a section just for joints. The reason I asked my question though, is because one photo shows the inside of the joint and the other doesn't. And they don't tell you what the difference is... except for $10

I got the interlocking one for the extra $10. I figured I wouldn't miss an extra $10.

Here's the latest Hogan Report...

Thanks to everyone for all your info & input. You're right, Curt responded first thing in the morning to my email, and he was helpful on the phone. I just finished talking to him and I ordered the DP & gaskets.

Now the interesting part...

I totally agreed that $10 is nothing, but I still wanted to know just what the mechanical difference was between the two joints. Now I know the semantics are sort of backwards, but the way he described it the "interlock" unit is more convoluted or corrugated on the inside, and the standard pipe is a smoother, interlocking pipe, like the flex pipe you see connecting header pipes to exhaust stacks on semi tractors. The upshot is that the standard pipe actually flows better...

Curt said that the main reason he started offering the second choice is that other companies are doing it so he had to do so, too. His opinion is that the longevity is at least the same, and his actual experience is that there is neither ticking nor whistling noises with the standard pipes that he put on all of his own Pontiacs.

So, I went with his recommendation to use the standard pipe (and yes, I told him VIN-1, supercharged.) At the very least, once I get it in we'll have some new information here for the forum.

(What I need here is an emoticon with fingers crossed...)

Quote :

I wouldn't think that header wrap would help the downpipe flex-joint if it did make noise, because the flexing would probably break or loosen the wrap...

For a noisy flex tube, the wrap helps immensely to attenuate ticking noise.

The wrap, if used in multiple, even layers of consistent tightness, should not break or loosen during everyday driving or track use. I've used the wrap for periods of over a year with no such issue.

What does tend to happen is the low hanging pipe makes contact with objects, snow, uneven ground, etc., which can fray the fibers and over time it can come undone. One solution is to coat the entire wrap with RTV, but even this can be damaged over time. What I've done is coat with RTV and used multiple (4) hose clamps to give support. Been installed about 2 years so far and holding up well.

Glad you found the Hogan pipe you needed. Hope it doesn't make any noise so you can skip the wrapping altogether!

AA wrote:

Glad you found the Hogan pipe you needed. Hope it doesn't make any noise so you can skip the wrapping altogether!

Well, as I inferred, I've got my fingers crossed... But if you can't trust the guy who builds them AND uses them, who can you trust?

I was poking around with a flashlight, trying to get some WD-40 on the exhaust bolts before the DP gets here, and another question occurred to me:

For you guys who have done the work yourselves, what wrench did you need for upper flange nuts? I have a long-handle swivel head ratchet and a couple different extensions, but I'm guessing that I'm gonna' have to buy a deep socket of some metric size, and I'd just as soon get it before I put the car in the air

Can't remember the socket size, but I'd use PB Blaster instead of WD-40. Much better penetrant, imo.

AA wrote:

Can't remember the socket size, but I'd use PB Blaster instead of WD-40. Much better penetrant, imo.

PB blaster now = easy job later

I don't recall exactly what combination of sockets etc I used to get the crossover off, but I didn't have to go get anything special...

deekster_caddy wrote:

AA wrote:

Can't remember the socket size, but I'd use PB Blaster instead of WD-40. Much better penetrant, imo.

PB blaster now = easy job later

I don't recall exactly what combination of sockets etc I used to get the crossover off, but I didn't have to go get anything special...

I think I've got enough things to combine, I just don't have any deep metric sockets... Does 17 or 18mm sound familiar for the downpipe/manifold flange?

I was thinking 15 at most...

deekster_caddy wrote:

I was thinking 15 at most...

Thanks. I just can't seem to eyeball metric...

The upper nuts are indeed 15mm, and the lowers are 9/16th's.

My final results... (with Pics!)

Well, I've learned a few things now that I've installed my own Hogan DP8S downpipe.

I was listening to the experiences of everyone here regarding noise__ Silent, ticking, tinging, pinging, etc. I admit that I missed something that Rickw said... Most everyone was centering on the flex-joint as the source of the noise, or perhaps leaks, myself included. He referred to the noise of the actual pipe, and I didn't catch the distinction...

I'm not saying that it's horrible, but it IS noticeable. It turns out that the reason the stock pipe looks pretty big on the outside (and weighs a ton) is because it is double-walled. Those same clever engineers who made several additions to the intake plumbing to virtually silence the un-Buick-like supercharger noises, did the same thing with the downpipe to prevent the pipe itself from "ringing", as it is ahead of the cat and receiving all the unmuffled exhaust pulses from the engine... Also, by mounting the original flex-joint up at the flange, they were able to weld a 'spout' to the flange that directs the exhaust gasses past the corrugations of the joint, rather than right across them...

Here are two photos of the factory and Hogan downpipes side-by-side:
http://farm3.static.flickr.com/2447/3552772391_73e5c9a1e1.jpg?v=0
http://farm4.static.flickr.com/3299/3552772387_8dda4538ee.jpg?v=0

Something else I learned that may help the next guy who tackles this job: With the car up on jack stands, the front suspension pulled down on the sway-bar and it was this close to the factory pipe. Thinking I'd need room until the wheels were back on the ground, I hassled with the sway-bar end-links to loosen them and rotate the bar away from the exhaust pipe... However, that clever Curt Hogan realized that the exhaust system has enough slack to push rearward, and the upper part of the pipe is almost an inch longer (see pic #1) than the original, and therefore lays the lower bend back far enough to leave MORE space than the original...

Oh, and like I said before, this is a California car - but to everyone who recommended PB Blaster, I had no
problems whatsoever, and the stuff is so strong that the overspray removed the undercoating from the friggin' body!

Mark, you said you noticed the noise, but did you notice anything else? Like a little more oomph in the gas pedal? Was the Hogan DP worth it?

I may have more oomph in first, but that was its strong suit before so it's hard to tell. Flooring it at the bottom of second though, around 40mph, it still feels slow, and at most it may have knocked a couple tenths off of my 0-60 time. I'd like to think it'll help my mileage, if I ever go back to keeping my foot out of it...

However, this was always a stepping stone anyway, as you, Ben and others strongly recommend the bigger downpipe for the smaller SC pulleys. I have driven it enough to decide to go ahead with a ZZP MPS... Last night I rented the puller and ordered the MPS with a 3.6" clearcoated pulley, so I'll be able to easily go further down or back up to stock with just the allen-wrench. It shipped this morning, so I should have it Monday night or Tuesday.

Oh, I should mention something that I only told Ben before: While theoretically I could go straight to a 3.5 or 3.4" pulley with the mods I've made this month, I'm not doing it because out here in EnviroNazi-land, the gas with the highest price in the country has the lowest octane - 91-octane piss-water, that'll probably be back up to $3 a gallon by next week...

I hear you, Mark. Going in slow is the best way. I think more of us should try the 3.6" SC pulley before moving smaller.

Any gains you got from installing the DP will be on the mid-high RPM side - the hardest to feel in the seat. When you get that MPS on, I think you will change your tune. The pulley is a low-end torque builder that you will definately notice. The good thing about installing the DP is that it lets power develop in the mid & high bands also, not just in the low RPMs.

AA wrote:

I hear you, Mark. Going in slow is the best way. I think more of us should try the 3.6" SC pulley before moving smaller.

Any gains you got from installing the DP will be on the mid-high RPM side - the hardest to feel in the seat. When you get that MPS on, I think you will change your tune. The pulley is a low-end torque builder that you will definitely notice. The good thing about installing the DP is that it lets power develop in the mid & high bands also, not just in the low RPMs.

Sounds good to me!

And maybe the pulley will also give more blower whine to cover up the downpipe...

Slightly higher pitch blower whine... If it's any louder, its' because your foot is too far in the pedal.

Well, I have one last thing (hopefully) to add to this thread because my MPS blower-pulley job has been delayed... ZZP sent out the rental puller with two 8mm studs and an 8mm pilot, all of which had been used and damaged! I could only thread one of them into the 5/8" shaft...

Today I had a chance to take what counts as a 'highway trip' in this congested hell-hole, and I came to two realizations: When Buapo told me how the 3-inch DP "woke up" his car, he'd already changed his supercharger pulley... so that makes perfect sense. And when AA asked me if I'd noticed more 'oomph', I hadn't really had a chance to test the upper RPM range.

On the flats, I wind through 1st so fast that any gain is imperceptible. Tonight, though, I happened to use an uphill onramp that led to another 1/4-mile of uphill highway before the road flattened out. I had my usual zing through 1st, and a bit of a lug in 2nd, then as I kept it to the floor climbing the hill I felt it surge when it passed 4200 RPM! I think I did an 80mph 1/4-mile, uphill... I certainly left everyone else from that onramp in the dust...

So, I'm happy to give them each a commendation, and hope to be even more complimentary when those damned screws for the pulley-er arrive... Cheers,

Well, I finally have my last mod finished!

I might recount it in one of the pulley threads, but this 2-hour job took 2 weeks because the puller I rented from ZZP was out of tolerance. It took days of emailing back & forth, with photos, to get all the new parts I needed to pull & press without breaking any studs...

However:
Ben, Aaron, you were both right about the package: this 3.6" pulley has 'woken up' the 3" downpipe, and filled in much of the "valley" in 2nd gear. I have about 2-2.5 degrees of KR at WOT, so I could probably go to a 3.5" even on 91-octane because I still have spark plugs up my sleeve (I'm still running heat-range-6...) I'll keep an eye out for a used ZZP or Intense 3.5.

Thanks for your help on this,
Mark

PS - I expected the 8-rib ZZP pulley to run on the center ribs, but after one crank it settled in on the outer set...

Mark, I think the SC belt should be in the middle grooves, not the outsides. Otherwise, check the belt's alignment down on the crank pulley. See link:

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/intense-vs-zzp-sc-pulleys-t971.htm

What happened to all the posts from last night and today?

See above link, page 4.

hey, so on 3800 performance they have the downpipe for our riviera.. what gaskets do i get for my 98, it says gt1 and gt3 but which gaskets are those exactly? same as bonnevilles? would it be cheaper to weld the 3 inch h body down pipe into my riv or buy gaskets and bolt it in... if so.. what gaskets do i need exactly?

1998 Riv wrote:

Curt Hogan replied to me this morning. Looks like I'll give this a try at some point, maybe later this summer.

Quote :

Thank you for the interest. Yes, our DP8S is a direct fit party for the Rivera in 97, 98 and 99 only.This pipe bolts to the factory manifold and to the inlet flange on the catalytic converter. Installation requires A GT1 gasket at the upper connection and a GT3 at the lower. If you are interested in purchasing these items the cost is as follows.
DP8S 139.95 plus 10.00 with optional interlock flex for tick and whistle free operation.
GT1 13.00
GT2 5.00
S&H 17.50 (Lower 48 States)
If you wish to order, please make PayPal payment to Belair427@cox.net
and we will ship within 48 hours.
Thank You
Curt Hogan
Hogan Performance

gt1 is the round crush at the back of the manifolds the gt3 is the square to the convertor. just put my hogan 3" on this weekend fit really nice better then the stock one actually.. other then the price i was really happy