Maggie Bypass problem
Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
Maggie Bypass problem
402 block with loads of mods, boost pressure is not rising because of Bypass opening right away when throttle is opened.
Quotre from Magnuson: "The bypass is operated by a vacuum actuator control unit that is normally closed. When vacuum is high (idle-cruising) the actuator opens the bypass valve, equalizing the vacuum pressure throughout the system. When boost is required (accelerating) the vacuum is decreased and the bypass valve instantly closes, causing pressure to increase into the cylinders."
Why is there so much vacuum after throttle body all the time when accelerating?
Quotre from Magnuson: "The bypass is operated by a vacuum actuator control unit that is normally closed. When vacuum is high (idle-cruising) the actuator opens the bypass valve, equalizing the vacuum pressure throughout the system. When boost is required (accelerating) the vacuum is decreased and the bypass valve instantly closes, causing pressure to increase into the cylinders."
Why is there so much vacuum after throttle body all the time when accelerating?
Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
..While the vacuum line to the Bypass actuator was disconnected, the boost pressure was only 3 psi.. How come? My calculations say that with 402 cid displacement, stock pulleys on MP122 Maggie the boost should be twice as much.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
402 block with loads of mods, boost pressure is not rising because of Bypass opening right away when throttle is opened.
Quotre from Magnuson: "The bypass is operated by a vacuum actuator control unit that is normally closed. When vacuum is high (idle-cruising) the actuator opens the bypass valve, equalizing the vacuum pressure throughout the system. When boost is required (accelerating) the vacuum is decreased and the bypass valve instantly closes, causing pressure to increase into the cylinders."
Why is there so much vacuum after throttle body all the time when accelerating?
Quotre from Magnuson: "The bypass is operated by a vacuum actuator control unit that is normally closed. When vacuum is high (idle-cruising) the actuator opens the bypass valve, equalizing the vacuum pressure throughout the system. When boost is required (accelerating) the vacuum is decreased and the bypass valve instantly closes, causing pressure to increase into the cylinders."
Why is there so much vacuum after throttle body all the time when accelerating?
How much vacuum are you measuring after the throttle body? Define "so much vacuum". I am wondering if you are assuming there is vacuum because the actuator isn't working properly. Have you verified that there are no vacuum lines that have even the smallest possibility of interfering with the physical movement of that actuator throughout its entire range of motion? If not, you need to because if that actuator isn't closing the valve completely or set properly and is allowing any air past the butterfly valve, it will kill your ability to make boost. You can remove vacuum from the actuator and verify that when there is no vacuum, it is going to the full closed position and if not, adjust it to where it is. Lastly, you may end up having to remove the snout to inspect the butterfly valve itself.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
You could have belt slip. It can slip at the crank, at the drive pulley and at the rear pulleys.
Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
Oh, I see. I was expecting much more boost from stock Maggie setup. How about this, I made a chart which is based on s/c cc, engine cc and other variables. Does this correlate to real life (if we do not count overlap from some cam that isn't suited for s/c use)?
www.tapanen.net/Maggie boost excel1.jpg
If it does, please correct me if I'm wrong with some variables (pulley sizes, s/c cc etc).
www.tapanen.net/Maggie boost excel1.jpg
If it does, please correct me if I'm wrong with some variables (pulley sizes, s/c cc etc).
Former Vendor
Joined: Jun 2009
Posts: 49
Likes: 0
From: Ventura CA
Not sure the all variables/units you are using in your calculator? But we stick with cu.in units, MP112 / 402 Vs. pulley ratio (+ little more math) = psi
PM me your e-mail address and I’ll send you our calculator. Anyone else want a copy? PM me…
We do have a few solutions to increase your boost, what is your psi. goal?
PM me your e-mail address and I’ll send you our calculator. Anyone else want a copy? PM me…
We do have a few solutions to increase your boost, what is your psi. goal?
Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
(Sent you PM Jason) In fact there's two different cases I'm interested of right now:
1. Forged 402 with many mods and a MP122 on top of it. My friends ride. Psi goal somewhere 15-20 psi.
2. Stock 346 ci with cam, headers, heads, T/B and a MP122 on top of it too. My ride. I haven't finished it yet so I don't know the boost I'm making. I assumed I would get 7 psi with MP112 and 9 psi with MP122 with stock pulleys but apparently I was wrong. That 9 psi is my goal.
That calculation I made was based on same math I used when I installed a Eaton M45 on my Beamer some years ago. That time theory and practise were the same and calculations became reality. After that I've calculated and fabricated pulleys for 2 other projects with success. This is the first time for me with magnuson products but the Eaton unit inside it seems to be the same family with that M45. I'm looking forward to have the official calculation base and I will adjust those base values on my calculations according to that.
1. Forged 402 with many mods and a MP122 on top of it. My friends ride. Psi goal somewhere 15-20 psi.
2. Stock 346 ci with cam, headers, heads, T/B and a MP122 on top of it too. My ride. I haven't finished it yet so I don't know the boost I'm making. I assumed I would get 7 psi with MP112 and 9 psi with MP122 with stock pulleys but apparently I was wrong. That 9 psi is my goal.
That calculation I made was based on same math I used when I installed a Eaton M45 on my Beamer some years ago. That time theory and practise were the same and calculations became reality. After that I've calculated and fabricated pulleys for 2 other projects with success. This is the first time for me with magnuson products but the Eaton unit inside it seems to be the same family with that M45. I'm looking forward to have the official calculation base and I will adjust those base values on my calculations according to that.
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Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
Thanks Jason! My mistake was that I believed what I read about 112 and 122 displacements.. I didn't know those model names were in fact their displacements in cubic inches
Now I corrected that and my chart shows 0,4 psi difference to yours! Must be that boost sludge factor but I'm happy with the result.
No wonder the boost was so low with that 402. Now I have to change my own pulley to 3,1 to get that 9 psi. My friend needs to go with 2,7 to be on the same psi.
But am I speeding with the s/c with that 3,1 pulley? With stock pulley at the crank@6200 rpm that makes 14700 rpm on s/c. That is acceptable, I suppose but how about my friend with that 2,7 pulley. That makes 16900 rpm on the s/c.. Is that too much?? I suppose a LS2 has the same diameter crank pulley as the LS1..?
Now I corrected that and my chart shows 0,4 psi difference to yours! Must be that boost sludge factor but I'm happy with the result.
No wonder the boost was so low with that 402. Now I have to change my own pulley to 3,1 to get that 9 psi. My friend needs to go with 2,7 to be on the same psi.
But am I speeding with the s/c with that 3,1 pulley? With stock pulley at the crank@6200 rpm that makes 14700 rpm on s/c. That is acceptable, I suppose but how about my friend with that 2,7 pulley. That makes 16900 rpm on the s/c.. Is that too much?? I suppose a LS2 has the same diameter crank pulley as the LS1..?
Former Vendor
Joined: Jun 2009
Posts: 49
Likes: 0
From: Ventura CA
You beat me to it (oatmeal break)…. Now we are in cc. for the TVS 1900 (116cu.in) & 2300 (140)
How do you like our calculator? It has the variable for the rear over drive, which is a BIG advantage on larger displacement engines…
The 402 @ 15+ psi. will want min. 8rib on the front or you WILL have slip issues & the 2.70” is a tight fit & little belt engagement… we do have a rear cog (see FUNCOOL) that can be adapted it’s TVS specific, but we make the parts to fit a 122
People have taken them to 25k, but for longevity we don’t (bearings not rated) recommend past 18k….
Yes, LS-2 & LS-3 are all 7.35” crank pulleys.
How do you like our calculator? It has the variable for the rear over drive, which is a BIG advantage on larger displacement engines…
The 402 @ 15+ psi. will want min. 8rib on the front or you WILL have slip issues & the 2.70” is a tight fit & little belt engagement… we do have a rear cog (see FUNCOOL) that can be adapted it’s TVS specific, but we make the parts to fit a 122
People have taken them to 25k, but for longevity we don’t (bearings not rated) recommend past 18k….
Yes, LS-2 & LS-3 are all 7.35” crank pulleys.
Racer
Joined: Jul 2008
Posts: 254
Likes: 0
From: Everett WA
Hey Jason, I've been battling with ye ol 112 on my forged 408 6.0. Right now I'm boosting about 5psi with a 3" pulley. I want to get into the 12-14 range and I wanted to do a 2.7 up front and rear overdrive. Can I purchase the rear setup as a package from you or do I need to source all the parts piece by piece?
Thanks!
edit: I forgot to mention I will be switching to all 8 rib and be using a larger crank pulley.
Thanks!
edit: I forgot to mention I will be switching to all 8 rib and be using a larger crank pulley.
Former Vendor
Joined: Jun 2009
Posts: 49
Likes: 0
From: Ventura CA
We do have a 30mm COG ‘kit’ (3.60”/3.0” overdrive) for the TVS, the MP112/122 just needs custom 2pc. hubs to make the 2pc. pulley fit. The hubs are designed, just need to be maid… not much (any) demand. There is a bit of work involved to press off the old pulleys and install the new ones…
We also have 2pc. front pulleys in 8 rib (2.8, 3.0 & 3.20”) the hub is specifically for the press fit shafts, but can make it work for ye ol keyed shafts
Not to dissuade you on 15psi (depending on desired HP) our motto is less boost & more timing…. So… boost on…
Jason
We also have 2pc. front pulleys in 8 rib (2.8, 3.0 & 3.20”) the hub is specifically for the press fit shafts, but can make it work for ye ol keyed shafts
Not to dissuade you on 15psi (depending on desired HP) our motto is less boost & more timing…. So… boost on…
Jason
Racer
Joined: Jul 2008
Posts: 254
Likes: 0
From: Everett WA
Would you happen to have any pricing information on the rear setup? Also, would a regular auto machine shop be able to remove the pulleys? I can't imagine it would be manufacturer specific or anything, right?
Basically I'm trying to weigh out the options of over driving the maggie or just selling it off and buying something else. I would like to continue with the maggie for its fast response.
Basically I'm trying to weigh out the options of over driving the maggie or just selling it off and buying something else. I would like to continue with the maggie for its fast response.
Former Vendor
Joined: Jun 2009
Posts: 49
Likes: 0
From: Ventura CA
what is your HP goal? what all parts do you have? 408cu.in. MP112, full exhaust system...etc.... 
you might be able to do the hub install yourself? all the parts are to size, no machining needed, so... if you have M8 tapped holes in the end of the shafts? (we did not have M8 threads in some) then you (with out a hydraulic press) can pull the hubs on 100% and if you do the old shrink fit trick to help get hubs on... your done...
got to reinstall the manifold assembly back on... and your done...
I'll have to turn you over to "BlownChevy" for the $$$'s???
Jason
you might be able to do the hub install yourself? all the parts are to size, no machining needed, so... if you have M8 tapped holes in the end of the shafts? (we did not have M8 threads in some) then you (with out a hydraulic press) can pull the hubs on 100% and if you do the old shrink fit trick to help get hubs on... your done...
got to reinstall the manifold assembly back on... and your done... I'll have to turn you over to "BlownChevy" for the $$$'s???
Jason
Racer
Joined: Jul 2008
Posts: 254
Likes: 0
From: Everett WA
I know its one of the newer intercooled models, but I'm not sure if its model with M8 threads.
Right now the engine has this...
408 cu 6.0 LQ9 (forged internals - h beam rods, -23 dish, etc..)
241 heads (ported/polished)
crane valve springs, titanium locks/retainers
crane quick lift 1.8 rockers
high volume oil pump
ceramic coated / heat wrapped short headers into full open exhaust
MTI Stealth II cam 224/220 581/581 116
LS2 snout / 90mm throttle body
fluidampr
I'm only looking to produce about 600 whp.. I'm not wanting any super high numbers as I wont be tracking the car much and it is more of a street car. When it had the LS1 at 12psi it was putting down into the mid 500's. At 5.5 psi it put down 489whp.
So I dont think its too much to ask to see 600ish
Right now the engine has this...
408 cu 6.0 LQ9 (forged internals - h beam rods, -23 dish, etc..)
241 heads (ported/polished)
crane valve springs, titanium locks/retainers
crane quick lift 1.8 rockers
high volume oil pump
ceramic coated / heat wrapped short headers into full open exhaust
MTI Stealth II cam 224/220 581/581 116
LS2 snout / 90mm throttle body
fluidampr
I'm only looking to produce about 600 whp.. I'm not wanting any super high numbers as I wont be tracking the car much and it is more of a street car. When it had the LS1 at 12psi it was putting down into the mid 500's. At 5.5 psi it put down 489whp.
So I dont think its too much to ask to see 600ish
Former Vendor
Joined: Jun 2009
Posts: 49
Likes: 0
From: Ventura CA
She needs more BOOST, Captain….. it’s typical to see 20hp per psi…. so…
http://www.magnacharger.com/images/dyno/402_CI_LS2.jpg
this is the only similar engine dyno graph I could find (except the 122 ) to make the #’s it’s most likely 100 octane & timing pegged…
what is you CR? & what intake / air filter you got?
http://www.magnacharger.com/images/dyno/402_CI_LS2.jpg
this is the only similar engine dyno graph I could find (except the 122 ) to make the #’s it’s most likely 100 octane & timing pegged…
what is you CR? & what intake / air filter you got?
Racer
Joined: Jul 2008
Posts: 254
Likes: 0
From: Everett WA
I'm using the 241 LS1 heads with the stock GM head gasket and -23 dish pistons, I can't remember what it came out to when we did the math but I want to say it was around 9:1
The intake I'm using is one of those big wide K&N set ups fed directly into the ls2 snout and 90mm TB.
I liked how my car was with the LS1 and 540ish whp ... if I can gain 100 hp from my forged motor with higher boost, I'll be happy leaving it as is.
The intake I'm using is one of those big wide K&N set ups fed directly into the ls2 snout and 90mm TB.
I liked how my car was with the LS1 and 540ish whp ... if I can gain 100 hp from my forged motor with higher boost, I'll be happy leaving it as is.
Former Vendor
Joined: Jun 2009
Posts: 49
Likes: 0
From: Ventura CA
I'm sure you saw this thread? http://forums.corvetteforum.com/c6-f...ess-power.html makes you think a little... I need to catch-up on the last few pages…
Cool, you got the K&N to fit... that is a BIG filter you don't have a water sock on it do you?
I should have asked, currently what is your total timing advance? & what octane fuel you have in Wa.?
Jason
Cool, you got the K&N to fit... that is a BIG filter
you don't have a water sock on it do you?I should have asked, currently what is your total timing advance? & what octane fuel you have in Wa.?
Jason
Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
2. Stock 346 ci with cam, headers, heads, T/B and a MP122 on top of it too. My ride. I haven't finished it yet so I don't know the boost I'm making. I assumed I would get 7 psi with MP112 and 9 psi with MP122 with stock pulleys but apparently I was wrong. That 9 psi is my goal.
Problems: So little boost and loads of ign retard due to knock issues.
I have a MP122 from LS2 fitted on stock LS1 bottom. Heads are ported LS1 with slightly bigger valves. Cam is Comp Cam 228/236 116 LSA, lift .588/.601. Exhaust is Kooks LT with Magnaflow X-pipe, 3", no cats. I have a 90 mm TB. Blower is with 3" pulley, crank pulley diameter is stock. No underdrive, nor overdrive behind the blower.
Boost rises only to 5 psi. And to that it needs 6000 rpm, below that its lower and above that it starts falling. I was expecting 10 psi.
I have a terrible knock issue too. Knock is there even with as low as 4 psi boost. With bypass valve open, boost rises only to 2-4 psi and works with decent ign advance but with a little boost, I have to retard a lot, to minus figures. From 800 rpm upwards it knocks with boost all the time. First noice you can hear from a "stetoscope" but after that it might be false knock..