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I'd like to get back on the same dyno once I get a few revisions on the tune under my belt. I'll keep tweaking and trying to find inefficiencies. I'd really like to copy Tchaps KPA in the log he posted. He has a twin screw and I thought my roots blower would build boost similar to his.
Glad you are getting some help on this mate.
Your KPa still doesn't look right to me. Your peak figure looks good, its just you should have that through way more of the rev range.
If you have a bypass already on the charger and it is working (looks like you do) it might be worth removing the blow off valve entirely from the system for some test runs, see if that makes any difference to pressure levels achieved earlier in the rev range. Go easy because if it does work you will be hitting areas of the map you haven't hit before, potentially in need of tweeking, so keep an eye on AFRs etc. Timing table looks ok in the areas I hope you would hit so that should be ok. Just replace the BOV tee silicone coupler with a straight coupler into the second tb.
Do you have any idea on the history of the supercharger? I don't mean to be the voice of dread but perhaps mis timed rotors or excess clearance to casing could cause this. At lower sc rpms the excess / incorrect clearance allows a larger proportion of air back past the rotors causing a lack of boost in the system. As sc rpm increase proportionally that leakage reduces and you get back to somewhere near the expected boost for this pulley ratio. Its just a theory - check the BOV first and try to see some more MP62 boost plots - but everything else seems to check out.
Your KPa still doesn't look right to me. Your peak figure looks good, its just you should have that through way more of the rev range.
If you have a bypass already on the charger and it is working (looks like you do) it might be worth removing the blow off valve entirely from the system for some test runs, see if that makes any difference to pressure levels achieved earlier in the rev range. Go easy because if it does work you will be hitting areas of the map you haven't hit before, potentially in need of tweeking, so keep an eye on AFRs etc. Timing table looks ok in the areas I hope you would hit so that should be ok. Just replace the BOV tee silicone coupler with a straight coupler into the second tb.
Do you have any idea on the history of the supercharger? I don't mean to be the voice of dread but perhaps mis timed rotors or excess clearance to casing could cause this. At lower sc rpms the excess / incorrect clearance allows a larger proportion of air back past the rotors causing a lack of boost in the system. As sc rpm increase proportionally that leakage reduces and you get back to somewhere near the expected boost for this pulley ratio. Its just a theory - check the BOV first and try to see some more MP62 boost plots - but everything else seems to check out.
You have me questioning the bypass valve. If the bypass was letting air past the rotors it would explain the missing pressure. I'll get a video up of the bypass valve and it's action when I blip the throttle. Idk much about them but it appears to work as it should. When I blip the throttle it closes and opens when the throttle closes. I have a brand new bypass valve but have not installed it. I would have already changed it but the allen bolts holding the bypass to the blower are on there super tight.
The history of the blower is pretty unknown. As I showed at the start of my thread I took it apart and it appeared to be in good shape. 95% Of the teflon coating is left on the rotors and the casing didn't have any anything that struck me a concerning.
Photo Dump:
I've been working on this car so much the past month I haven't had a chance to wash it but found the time this weekend. I had to take a few shots.
Would expect to see MAP to build to maximum by say 4krpm and the basically remain within a few kpa until redline.
At one point, I was running the same intake manifold as the OP(and head) and noticed a 2psi increase from 5500rpm to 7000rpm. This was with a larger
supercharger running higher boost, however I would still expect a rise over this rpm range with the OP's setup and boost levels. (This manifold does not flow well, which results in rising boost above 5500rpm)
From what I have read, 13 PSI near redline is typically reported for this pulley set up with stock engine and slightly better than stock exhaust.
Originally Posted by Cincykemo
You have me questioning the bypass valve. If the bypass was letting air past the rotors it would explain the missing pressure. I'll get a video up of the bypass valve and it's action when I blip the throttle. Idk much about them but it appears to work as it should. When I blip the throttle it closes and opens when the throttle closes. I have a brand new bypass valve but have not installed it. I would have already changed it but the allen bolts holding the bypass to the blower are on there super tight.
You need to confirm that the bypass closes properly. To do this, disconnect the hose going into the bypass valve while the engine is idling. If the blower starts making a horrible moaning sound, and the engine begins to labour, then the valve is closing properly.
(This noise is normal for this style of supercharger and running it with the bypass closed for a short while like this will not do any damage). If I were you, I would connect and disconnect this hose a few types with the engine running, just to ensure the valve is closing reliably.
You need to confirm that the bypass closes properly. To do this, disconnect the hose going into the bypass valve while the engine is idling. If the blower starts making a horrible moaning sound, and the engine begins to labour, then the valve is closing properly.
(This noise is normal for this style of supercharger and running it with the bypass closed for a short while like this will not do any damage). If I were you, I would connect and disconnect this hose a few types with the engine running, just to ensure the valve is closing reliably.
Just throwing out some random other things to check. The kpa log looks a little like belt slip. I could be wrong.
Engaging the bypass valve like in the video is okay, but small leaks would be tested by holding vacuum. Like move the bypass arm and stick your finger on the barb and ensure it stays fixed in vacuum.
Whenever I see an older, bare aluminum pulley, I assume it's an original BRP version, and they tend to get passed down. But they were sometimes cut with a bad angle, that's been diagnosed to slip.
Lastly, if you do check the bypass, make sure the "stop" on it is correct. Uncommon problem, but it can happen is someone takes a bypass valve swap for granted. Need to make sure when boost is applied the throttle is fully closed.
^that's a great video for setting up the bypass. From the OP's video, it looks/sounds like the valve is closing, but it's still worth doing a quick check though.
In the screen shot above, the RPM is also stepping up, along with the MAP. It looks like this section of the trace, includes a down shift?
Just throwing out some random other things to check. The kpa log looks a little like belt slip. I could be wrong.
I see it and I could certainly see that being caused by a belt slip event.
Originally Posted by RunninOnEmpty
Whenever I see an older, bare aluminum pulley, I assume it's an original BRP version, and they tend to get passed down. But they were sometimes cut with a bad angle, that's been diagnosed to slip.
I'm actually running an anodized TDR pulley atm. The only time I used the BRP pulley was my first dyno session. Thanks for the thread, it was very informative and I learned a lot. I have been using a cheap belt (only one I could find in 48.8 in) but finally found a Gates RPM belt I have coming in soon to replace it.
Originally Posted by RunninOnEmpty
Lastly, if you do check the bypass, make sure the "stop" on it is correct. Uncommon problem, but it can happen is someone takes a bypass valve swap for granted. Need to make sure when boost is applied the throttle is fully closed.
I watched this same video before I set up the bypass stopper. At the time I had the outlet manifold and throttle body off the blower and used a light shined through the rotors to make sure the bypass was fully closed when I set the stopper. Out of all the things I did I'm confident in having set this correctly.
Originally Posted by oreo
In the screen shot above, the RPM is also stepping up, along with the MAP. It looks like this section of the trace, includes a down shift?
No downshifts in that log. I was in 2nd and then put it in 3rd around 1,500rpm before I went WOT for that log.
Do you have any idea on the history of the supercharger? I don't mean to be the voice of dread but perhaps mis timed rotors or excess clearance to casing could cause this. At lower sc rpms the excess / incorrect clearance allows a larger proportion of air back past the rotors causing a lack of boost in the system. As sc rpm increase proportionally that leakage reduces and you get back to somewhere near the expected boost for this pulley ratio. Its just a theory - check the BOV first and try to see some more MP62 boost plots - but everything else seems to check out.
I reached out to Tom at FFS and received this information back regarding a possible "bad blower."
"My history shows that the MP62 makes same boost/power until the day it stops turning.Loss of boost/power is typically a loose/slipping belt or a bypass valve that is not closing completely." -Tom
I had my first remote tuning session yesterday. I was still running primarily on the tune from the very first tuner who dyno tuned the car. This new tuner tweaked that tune and that's what I have been running for the past couple of weeks. Yesterday we did idle, regular drivability and then at the end of our session he sent me the revision I did this 3rd gear WOT log on. When he said my old tune was "very aggressive" up top I was worried I'd loose the top end which was the only part of the power band that was really satisfying to me on this setup currently. To my surprise the car felt the same with the new safer tune down low and up top. I was told the timing was so aggressive up top that more than likely it had passed it's most efficient setting explaining why less timing felt the same.
I got to have some fun the other day with a new Supra. On the way into work he flew up on my tail passed and I gave chase. We had a couple of good pulls in between us when we had safe gaps. 3rd Gear was great and I stayed pretty even with him up into 4th. I'd imagine he would really start pulling on me here but I wasn't comfortable doing that speed on that road so I never found out. Good stuff.
Whenever I see an older, bare aluminum pulley, I assume it's an original BRP version, and they tend to get passed down. But they were sometimes cut with a bad angle, that's been diagnosed to slip.
I replaced my off brand belt with a Gates RPM. You can see the peaks of the pulley don't make contact with the belt on the Gates (bottom pic) but do on the off brand (top pic.)👌
I reached out to Tom at FFS and received this information back regarding a possible "bad blower."
"My history shows that the MP62 makes same boost/power until the day it stops turning.Loss of boost/power is typically a loose/slipping belt or a bypass valve that is not closing completely." -Tom
That's fair enough. I was thinking maybe it had been dodgily repaired in the past, say rotors seized and then had the housing honed out to remove any gouging. But it all seems a bit unlikely.
Hopefully the issue is some belt slip or bypass related stuff.
Have you asked TDR if they have a plot of boost vs RPM for that combo? I have worked with them a few times in the past and found them to be quite helpful.
Have you asked TDR if they have a plot of boost vs RPM for that combo? I have worked with them a few times in the past and found them to be quite helpful.
I sent out an email asking this same question to Gary this morning.
After getting my log in the email this morning he responded: "Boost is nice and linear so looks spot on."
Idk at this point. I messed up not going turbo I guess.
I realize that Tom is probably a decent source of historical knowledge on these things, but man, I really have trouble dealing with his "technical" posts. I'm glad he started his own forum
This looks like fun, subb'd. Good luck with your pile of whatsit there hamstray
I replaced my off brand belt with a Gates RPM. You can see the peaks of the pulley don't make contact with the belt on the Gates (bottom pic) but do on the off brand (top pic.)👌
Coolio. On the first post/photo I saw a huge aluminum crank pulley at the top left. Are the teeth on that one pretty decent, like OEM or really peaky?
I realize that Tom is probably a decent source of historical knowledge on these things, but man, I really have trouble dealing with his "technical" posts. I'm glad he started his own forum
Oh man, yeah. He seems like a decent guy, and I really appreciate the fact that he offers a unique solution, but there have been a few occasions where I felt obligated to correct the nonsense he has posted.
Threw all my belts on the way into work. Crank pulley is loose but has all the bolts still in it. I really hope those bolts didn't shear. The bolts are the allen head bolts supplied with the supercharger crank pulley and I was never super happy with the way they felt when I tightened them, very vague feeling. O well, another day to spend in the driveway on an off day.
Got around to figuring out what happened yesterday. The crank bolt was loose and the woodruff key was cracked. I had noticed a low rpm crank pulley wobble a month ago but it didn't appear to be super bad. I tightened the crank bolt at the time (it didn't appear loose) to see of that would solve the issue, it didn't. The wobble always went away at a slightly higher rpm so I ran it this way anyway.
Getting the timing gear off was a little difficult. I heated it with a propane/butane torch and wedged a chisel behind it. Once I got it a little separated I used a two jaw puller. Luckily the keyway looks good although it's a little worn at the end but I don't think it'll be an issue. Now I'm waiting on parts. I just would hate to put everything back together and still have the same crank wobble. With the 6 rib additional pulley I know it's introducing more stress on the entire pulley assembly but as long as the 6 rip pulley is balanced correctly I don't feel it SHOULD cause an issue.
Now that the blower is off (for the 50th ******* time) it'll give me a chance to reconfirm my bypass valve stopper is set correctly.
09-05-2021, 03:00 AM
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