[Camaroking98]

I have a magnuson 2650 swapped on. I have an 80mm upper and 10.35 lower. How much boost should I be making?

For reference, last time I had a 75mm upper and 9.45 lower that made 16psi in my crappy DA. I was having belt slip though so we decided to go with a bigger upper and lower.

[Joshinator99]

Originally Posted by Camaroking98

I have a magnuson 2650 swapped on. I have an 80mm upper and 10.35 lower. How much boost should I be making?

For reference, last time I had a 75mm upper and 9.45 lower that made 16psi in my crappy DA. I was having belt slip though so we decided to go with a bigger upper and lower.

Your 75mm (2.95”) upper and 9.45 lower was netting you 20,822 RPM blower speed at 6500 RPM and a pulley ratio of 3.20 which is aggressive. I’m not surprised on the belt slip with the stock LT4 tensioner. Your new combo of 80mm (3.15”) upper and 10.35” is even more aggressive at 3.29 ratio and 21,357 RPM blower speed. In my experience, that pulley change won’t fix your problem.

You might want to look at TooHighPSI’s LT5 tensioner and 10-rib upgrade which I run on my combo (18 psi). The LT5 tensioner has more tension and greater travel…just a better piece across the board.

Hope that helps.

[Camaroking98]

Originally Posted by Joshinator99

Your 75mm (2.95”) upper and 9.45 lower was netting you 20,822 RPM blower speed at 6500 RPM and a pulley ratio of 3.20 which is aggressive. I’m not surprised on the belt slip with the stock LT4 tensioner. Your new combo of 80mm (3.15”) upper and 10.35” is even more aggressive at 3.29 ratio and 21,357 RPM blower speed. In my experience, that pulley change won’t fix your problem.

You might want to look at TooHighPSI’s LT5 tensioner and 10-rib upgrade which I run on my combo (18 psi). The LT5 tensioner has more tension and greater travel…just a better piece across the board.

Hope that helps.

Yes, I have that upgrade. It's their 10.35 (28%) lower and 10 rib kit with a griptec 80mm upper

[Joshinator99]

Originally Posted by Camaroking98

Yes, I have that upgrade. It's their 10.35 (28%) lower and 10 rib kit with a griptec 80mm upper

That’s the kind of info that would have been helpful to know lmao

Where is the tensioner in its travel range? The belt should be tight as heck to put on (it’ll loosen up a tick once you start running it hard).

[Camaroking98]

Originally Posted by Joshinator99

That’s the kind of info that would have been helpful to know lmao

Where is the tensioner in its travel range? The belt should be tight as heck to put on (it’ll loosen up a tick once you start running it hard).

Not sure on where its at in the travel range. I know prior we had it in the 50-60% range per magnusons suggestion with the 8 rib. Just slightly concerned because when they tested it today my friend said it made 12 pounds...the goal with this switch to was to make about the same amount of boost or a tad more with no slip. I also know DA was like 11-12k today so I'm not sure how much extra that effects it. The last day we tested with a log it was like 10k DA and we had 15 pounds of boost before falling off to 11 because of slip.

[Joshinator99]

Originally Posted by Camaroking98

Not sure on where its at in the travel range. I know prior we had it in the 50-60% range per magnusons suggestion with the 8 rib. Just slightly concerned because when they tested it today my friend said it made 12 pounds...the goal with this switch to was to make about the same amount of boost or a tad more with no slip. I also know DA was like 11-12k today so I'm not sure how much extra that effects it. The last day we tested with a log it was like 10k DA and we had 15 pounds of boost before falling off to 11 because of slip.

Doesn’t sound like the belt is tight enough IMO

[Camaroking98]

Originally Posted by Joshinator99

Doesn’t sound like the belt is tight enough IMO

how tight is tight enough? lol. I'm kind of inexperienced myself and rely on the expertise of others...I just order recommended parts

[laynlo15]

I have the THPSI 10 RIB with 9.25 lower and 95mm Griptech upper and mine makes 11 to 11.5 so I'd say your in that 12 to 13 psi area. Did your friend log your car on the dyno? Most of the logs are based on Kpa. So my Kpa on the logs from the track range from 175 to 180 on the Kpa.

[Joshinator99]

Originally Posted by laynlo15

I have the THPSI 10 RIB with 9.25 lower and 95mm Griptech upper and mine makes 11 to 11.5 so I'd say your in that 12 to 13 psi area. Did your friend log your car on the dyno? Most of the logs are based on Kpa. So my Kpa on the logs from the track range from 175 to 180 on the Kpa.

No way. His pulley combo is way more aggressive than yours. You’re at 16,900 RPM blower speed and a 2.60 ratio…if you get belt slip you’ve got serious problems LMAO

[Joshinator99]

Originally Posted by Camaroking98

how tight is tight enough? lol. I'm kind of inexperienced myself and rely on the expertise of others...I just order recommended parts

Mike Sitar (TooHighPSI) told me that if you can barely get the new belt on, that’s perfect…! And he was right. I did that and after running the car for a little bit I noticed the tensioner came down off max tension very quickly. I’m probably 75% tight right now and don’t seem to have any slip (9.25/3.25).

[Camaroking98]

Originally Posted by laynlo15

I have the THPSI 10 RIB with 9.25 lower and 95mm Griptech upper and mine makes 11 to 11.5 so I'd say your in that 12 to 13 psi area. Did your friend log your car on the dyno? Most of the logs are based on Kpa. So my Kpa on the logs from the track range from 175 to 180 on the Kpa.

Not dyno logged. But we are going to be logging it tommorow, just not on the dyno. We know how to read the log though so that should tell us enough.

[Camaroking98]

Originally Posted by Joshinator99

Mike Sitar (TooHighPSI) told me that if you can barely get the new belt on, that’s perfect…! And he was right. I did that and after running the car for a little bit I noticed the tensioner came down off max tension very quickly. I’m probably 75% tight right now and don’t seem to have any slip (9.25/3.25).

Hopefully mine works as planned. I know with my old pulley combo I made 15-16 true boost colorado. With this setup that's a tad more aggressive I'm hoping 17-18 true boost

[Camaroking98]

Update. Made 17.4lbs @87 degrees outside in this crazy high DA. Belt started fray. Issue is belt length had to be a 12 rib with 2 ribs cut off. They think there was an error in their cutting so they're ordering a special cutting tool and new belts to make it work per THP advice. And finally, no slip on the log. So that's definitely progress!

[JSH]

Originally Posted by Camaroking98

Not sure on where its at in the travel range. I know prior we had it in the 50-60% range per magnusons suggestion with the 8 rib. Just slightly concerned because when they tested it today my friend said it made 12 pounds...the goal with this switch to was to make about the same amount of boost or a tad more with no slip. I also know DA was like 11-12k today so I'm not sure how much extra that effects it. The last day we tested with a log it was like 10k DA and we had 15 pounds of boost before falling off to 11 because of slip.

This new DSX idler bracket tensioner is working well for me