Jim_H

So what do we need to do, Tim? A concensus on the diameter I suppose followed by how many of us want one?

Tony

thanks, great read

Another alternative to a bigger pulley is obviously a smaller upper pulley. The limiting factor as the system sits now is belt rap. DRs is the bench mark for that with his TS set up. With some work, with our original set ups, i think you could actually make another idler pulley that would anchor to the snout support pushing the belt farther around underneath....more wrap.

The upper pulley i have now is 2.59" as measured with an caliper, this gives 7-8psi...im only looking for another 3psi ...what decrease in upper diameter will give me that, im not exactly sure??
Darrien just got a 2.375 ( it think thats what it was) and to me it looks as if a belt would still be able to "hang in there".

For the cost of making and maching a bigger lower pulley, you may be able to channel resources and make another idler/tensioner on the snout support closer to the SC pulley instead.

just and idea/option?

Right now, there is nothing wrong with my accesory belts or how they run. If i can get the boost i want with out too much belt slip on a slighly smaller pulley, then the system the way it sits is fine for my application.

DR

Tony,

I was just looking at my idler setup and thinking about your comments.

From looking at it carefully I would swear you could bolt up my idler plate and put the idlers on the inside of the plate (between my plate and your existing one) and it would work perfectly. The belt even clears the standoffs required between your plate and my plate that bolt thru to the WP. Actually one of the idlers would be used as a "standoff" (lower pass. WP Bolt) and give even better crank wrap than I have.

Shane

That is interesting, because when I mounted up the 2" pulley on the whipple (smallest they make) I got nothing but A LOT of smoke after 3k rpms. Would have been nice to see what kind of boost was achievable with that small little bugger.

DR

Shane,

I have tested a 2.1" on my idler setup and the only smoke I got was from the TIRES

Bill Ball

Observations today from some dyno tuning of the SC related to a DEVEK X-over install....

Strange stuff:
1. Moving the vacuum source for the SC's bypass valve from Andy's chosen location of the intake manifold to a source on the throttle housing reduced low end torque by 20 lb-ft. Moving it back to Andy's location instantly restored the lost torque but caused the car to miss on idle again. Disconnecting the bypass vacuum line altogther (closing the bypass) fixed the idle and left the low-end torque up.
2. Driving around with the bypass valve disconnected so that it was closed all the time seemed to have no effect. In fact, the manifold vacuum/boost seemed to behave the same regardless. I expected that without the bypass, if I took my foot off the gas at 6000 RPM I would have boost galore still going into the coasting engine, but the manifold read 25 in vacuum. At idle, 20 in., bypass or not. I reconnected the bypass as it seems that with positive displacement blowers, you should need one, but I don't get the manifold readings I see with or without it.

Embarrassing stuff:
My A/F curves were very erratic today. One dyno run would be fine. The next would be fine down low but lean out to 15 at high RPM. Then it would be the opposite, lean down low and fine up top. This made the power curves erratic. And this is with no changes to the fuel system. At one point we replaced the 85 regulator with a Kirban RRFPR and we got the same wierdo erratic results. Then Marc asked me when I last changed my fuel filter. Uh, well, uh, you see, uh, I have one at home, uh, well, uh, the PO had it done as part of the 60K mile service, so, yeah, uh, yeah, well, I have a new one at home. Probably should change it as it's been in there 95K miles. Good point, Marc.

Then Marc asked me if I had ever checked the in-tank fuel pump. Well, uh, I checked the one in George Suennen's car, and, uh, yeah, the rubber hose was split 3/4ths of the way and the pump was kinda dangling there, but no, um, my pump is original. Yeah, right, I suppose at 155K miles it deserves a look-see considering how often that hose is found to be split.

Nice stuff:
So, even though we had a bit of trouble with erratic A/F curves, the DEVEK X-over with Randon Technology cats provided 26 HP (332 today before versus 358 after) and 35 lb-ft of torque. You may recall I have been quoting 345RWTQ since the SC install last year. The torque curves were different today from last year, both before and after the X-over. On the best runs with good A/F ratios, it peaked at 4700 RPM at 353 lb-ft versus 318 before. Now, the curve actually showed peak torque of 380 lb-ft!! at 2500 RPM, but Marc said that is not a valid number having something to do with the torque converter at low RPM range, and to only evaluate torque above about 3000 RPM. 2500 RPM is where I had 345 last year and today. I'd rather we use those numbers (380/345), but Marc said no. Still, the torque increase was 30-35 lb-ft throughout the entire curve, no matter where you chose to look. The curves were almost parallel. I will scan in a dyno run later.

The x-over changes the exhaust sound a lot. It changes the blub-blub pulses typical of a V8 muscle car (when you have a RMB) into a more even, nasty, raspy note. With the extra 30-35 lb-ft of torque, my stock rear tires are now a compete waste of time.

heinrich

Bill that is very interesting! Something sounds wrong there .....

mspiegle

Good report! That's definately some interesting info you've got there. So, if you forced the bypass valve closed at idle - your car didn't make strange noises? The engine wasn't rocking hard in the engine bay? That's very strange. On my 86.5 without the bypass valve, the car sounded very different at idle, and the engine rocked alot. On Chris' car, you could tell it wasn't running quite right, but it wasn't as pronounced as my car. I think the technical term is 'pump cavitation', where the pump is the SC unit itself.

The torque below 3k rpms is created by the torque converter multiplication. If you check the supermodel site for Andy's "latest" dyno, you'll notice 450rwtq at 2000rpm. As Marc said, just discard that part.

It was interesting to see the torque difference while changing the bypass valve. I bet the bypass is closing later in the situation with less torque.

Nice gains from the x-pipe! Sounds like you have a couple maintence items to take care of. Which dyno did you use?

Bill Ball

Mike:

I could see/hear/feel no difference at all, bypass hooked up to vacuum or just left atmospheric (closed). I drove around for 10 minutes that way and we did all the latter dyno runs that way.

OK, so I will ignore the torque level at 2500 RPM.

We used the same dyno and same parameters as last year at the SC install party.

The x-pipe was very successful. We are not comparing the worst before with the best after, considering my erratic A/F numbers. We used the best from each and the gains were quite good at 26RWHP and 35RWTQ. The thing I really like is the gains were throughout the RPM range.

IcemanG17

Bill
It seems your results are pretty close to the gains the Xpipe produced on a stockish S4....25/30 if I remember correctly (a challenge).... You gotta post a graph! So with the pump-filter checked you should gain even more? Maybe 370-380 or so? Time to get some wider rear tires & put in the limited slip! You gotta take that ride to the 1/4 mile track! My guess is 12's for sure!

Rick Carter

Using the SMT-6 to fine tune my 85 Eaton with 6.5 pounds of boost 1 degree of timing was pulled from 1970 RPM to 2700 RPM (77% - 100% deflection, this is a percent of 5 volts, 80%+4 volts etc.) with 2 degrees pulled at WOT 1970 RPM. These were the only places where timing was less than stock. If you have tip in problems this may help.

Bill Ball

Rick: Fortunately, I've never had tip-in issues.

Brian: See this thread for the dyno chart. The numbers were actually 28 HP and 32 TQ.
https://rennlist.com/forums/928-forum/249567-devek-x-over-results-in-my-89-a.html

Rick Carter

Bill,
As far as I know only some GTs have had a problem with tip in that was "corrected" by adding a ton of fuel. I don't have personal knowledge so I could be completely wrong. Retarding timing by 1 or 2 degrees may be a better solution if someone is not as fortunate as you. Did you get 5.1 installed yet? Mine sounds great but there is some noise I'm trying to track down and eliminate.

Bill Ball

Rick: Yes, I agree. Adding fuel is not the solution to tip-in. Either bleeding off some early boost or retarding timing to avoid it is a better answer.

I had the 5.1 installed and then the headunit went out. It is a Pioneer AVH 7500DVD that does it all including DVD-Audio, DTS, TV, XM radio. In for repair under warranty. Hey, those JBL P422 are great, but other than 1 pair on eBay, they are no where to be found any more. I have found some good alternatives (Audiobahn AS40Q) that are inexpensive on eBay. My biggest problem has been the 6.5" rears. The JL 6W0 did not perform well there, just kind of vibrating. I've tried all kinds of things to make a smaller sealed chamber behind them, but they never did the sub job. Interstingly, some MB Quart PCE216 6.5" speakers did really well, with some polyester stuffed in the body cavity. A small sub works best, but these speakers will make that unnnecessary in the end, I believe. The other issue is that the highs with all of the aftermarket tweeters I have tried are far too scratchy/bright. Silk dome tweeters are better than aluminum, etc., but all require a LOT of roll-off at the top. The Pioneer has a gajillion audio adjustments and gets the sound so that most people would think it is fantastic. It's close. I currently has a 3.5" stuffed in an adapter plate I made for the center vent. Not right, but at least I have a center speaker and it could be made workable with cosmetic finishing, and the vent still blows around the speaker.

Once I finish the 5.1 I will post my results and learnings in a new thread.

You have alternator whine?

Rick Carter

That seems to be what it is. Do you have a solution? The standard - moving all the RCA cables around, same size wires, common ground etc. has not been 100% effective.