MP62 - Not faster than stock!? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Supercharger Discussion For all you misguided souls.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 05-28-2016, 10:51 PM   #1
Junior Member
Thread Starter
 
Join Date: Nov 2011
Location: Ottawa, Ontario, Canada
Posts: 105
Total Cats: -1
Default MP62 - Not faster than stock!?

Posting for a friend:

Having issues with a newly installed MP62 kit on a 94 miata. Running a Moss Fuel card and a Jackson Boost Timing Controller. All settings to manual recommended modes. Also running dual throttle bodies and an intercooler. No afr guage now, but coming shortly.

The car produces the expected 7 psi of boost, but is not any faster than a stock miata in a straight line under WOT.
The vacuum is fluctuating strangely. Under cruise, it is normally about -12, but a light application of throttle, and the vacuum drops to -3 approx.
When lifting off from acceleration, a pffft air sound can be heard from under the hood.

Pulled plugs, and they looked fine. Compression and leak down tests were okay before install.

Realize that the first obvious step is to get some a/f readings, but any suggestions of things we should look at to check?

Thanks guys!
Frenchmanremy is offline   Reply With Quote
Old 05-29-2016, 02:10 AM   #2
Junior Member
iTrader: (2)
 
Join Date: Oct 2014
Location: Alberta, Canada
Posts: 68
Total Cats: 0
Default

The bypass valve unit / bypass arm seems to be a weak link, may be worth checking that that's functioning properly and not cracked/damaged. Sometimes the bypass arm doesn't retract and can get stuck too.
k1l4m is offline   Reply With Quote
Old 05-29-2016, 09:02 AM   #3
Junior Member
 
guttedmiata's Avatar
 
Join Date: Sep 2012
Posts: 438
Total Cats: -4
Default

He has a boost leak
guttedmiata is offline   Reply With Quote
Old 05-29-2016, 10:14 AM   #4
Elite Member
iTrader: (17)
 
Join Date: Aug 2007
Location: Fort Myers, FL
Posts: 2,651
Total Cats: 106
Default

Is the 7psi boost reading coming from the intake manifold? If it is, I would think that points to something other than the last 2 posts. Let us know what you find.
pdexta is offline   Reply With Quote
Old 05-29-2016, 11:07 AM   #5
Senior Member
iTrader: (2)
 
williams805's Avatar
 
Join Date: Oct 2013
Location: Goleta, Southern California
Posts: 502
Total Cats: 25
Default

If you're seeing 7 psi at the intake manifold, stop driving it. Get a afr gauge.

Im going to assumed you used spade terminals to hook those cards up. Pull each one apart and see if any of the spades are bent and not making contact.
williams805 is offline   Reply With Quote
Old 05-29-2016, 12:20 PM   #6
Junior Member
 
guttedmiata's Avatar
 
Join Date: Sep 2012
Posts: 438
Total Cats: -4
Default

Quote:
Originally Posted by pdexta View Post
Is the 7psi boost reading coming from the intake manifold? If it is, I would think that points to something other than the last 2 posts. Let us know what you find.
I didn't even notice he said it was making 7psi. Also stated is 12lbs of vacuum at cruise and 3lbs on light throttle.

At what point does it make 7psi of positive pressure? This isn't making sense.
guttedmiata is offline   Reply With Quote
Old 05-29-2016, 02:55 PM   #7
Senior Member
iTrader: (2)
 
Join Date: Dec 2011
Posts: 1,372
Total Cats: 128
Default

Quote:
Originally Posted by guttedmiata View Post
I didn't even notice he said it was making 7psi. Also stated is 12lbs of vacuum at cruise and 3lbs on light throttle.

At what point does it make 7psi of positive pressure? This isn't making sense.
The bypass on the compressor will not close unless manifold vacuum gets below a certain point (theoretically zero, but can be more like -1 to -2), so it is totally possible, and normal, to be able to drive and cruise without ever invoking the compressor, provided you don't lead foot it. This is how they were able to pass CARB on these, since the system is never really active under light driving/ smog test conditions.

I too suspect a bypass valve issue, as they are a known wear item. http://trackdogracing.com/supercharg...uatorunit.aspx
good2go is offline   Reply With Quote
Old 05-29-2016, 04:30 PM   #8
Senior Member
iTrader: (2)
 
williams805's Avatar
 
Join Date: Oct 2013
Location: Goleta, Southern California
Posts: 502
Total Cats: 25
Default

Mine just failed. The diaphragm ripped. This is typical.

When the diaphragm rips the bypass actuator will not open the bypass butterfly. There is a spring holding the bypass butterfly closed. This means the supercharer is always trying to make boost (even at idle). In other words, if the bypass actuator has failed in the typical fashion, it won't cause low boost. It will cause a no bypass situation.
williams805 is offline   Reply With Quote
Old 05-29-2016, 08:52 PM   #9
Junior Member
Thread Starter
 
Join Date: Nov 2011
Location: Ottawa, Ontario, Canada
Posts: 105
Total Cats: -1
Default

As far as I know he makes 7psi on the boost gauge, which is connected to the back of the intake manifold, if he had a boost leak, he wouldn't show positive pressure at the intake.

He is wiring an afr.

We checked all connections and fittings/vacuum hoses. All checks out.
He will be changing out the bypass valve just to rule it out.

Any input?
Frenchmanremy is offline   Reply With Quote
Old 05-29-2016, 09:00 PM   #10
Senior Member
iTrader: (2)
 
Join Date: Dec 2011
Posts: 1,372
Total Cats: 128
Default

Quote:
Originally Posted by Frenchmanremy View Post
As far as I know he makes 7psi on the boost gauge, which is connected to the back of the intake manifold, if he had a boost leak, he wouldn't show positive pressure at the intake.

He is wiring an afr.

We checked all connections and fittings/vacuum hoses. All checks out.
He will be changing out the bypass valve just to rule it out.

Any input?
If the bypass is failing, but not dead, he can make boost, but probably not hold it reliably. Also, the synchronization of the dual TB's, as well as the off-throttle butterfly position on the SC TB can make a huge difference in "air noises" made both on and off throttle.

.02
good2go is offline   Reply With Quote
Old 05-29-2016, 09:41 PM   #11
Junior Member
Thread Starter
 
Join Date: Nov 2011
Location: Ottawa, Ontario, Canada
Posts: 105
Total Cats: -1
Default

Quote:
Originally Posted by good2go View Post
If the bypass is failing, but not dead, he can make boost, but probably not hold it reliably. Also, the synchronization of the dual TB's, as well as the off-throttle butterfly position on the SC TB can make a huge difference in "air noises" made both on and off throttle.

.02
It holds 7psi steady, just not going any faster...
Frenchmanremy is offline   Reply With Quote
Old 05-29-2016, 10:01 PM   #12
Elite Member
 
Join Date: Apr 2010
Location: Newcastle, Australia
Posts: 2,585
Total Cats: 21
Default

Quote:
Originally Posted by Frenchmanremy View Post
It holds 7psi steady, just not going any faster...
The tune is completely fucked, obviously.
nitrodann is offline   Reply With Quote
Old 05-29-2016, 10:07 PM   #13
Junior Member
 
Join Date: Sep 2013
Posts: 193
Total Cats: 7
Default

there needs to be somethings looked at if the Intake manifold is seeing boost

maybe it's super lean and knocking
restriction in exhaust
super rich and (I'd assume you'd notice it miss firing)
timing is super low

something is not right I don't know how people have the guts to go wot without a wideband

you need a wideband before you can judge anything
Shortpersonbk is offline   Reply With Quote
Old 05-29-2016, 11:46 PM   #14
Senior Member
iTrader: (2)
 
Join Date: Dec 2011
Posts: 1,372
Total Cats: 128
Default

Quote:
Originally Posted by Shortpersonbk View Post
there needs to be somethings looked at if the Intake manifold is seeing boost

maybe it's super lean and knocking
restriction in exhaust
super rich and (I'd assume you'd notice it miss firing)
timing is super low

something is not right I don't know how people have the guts to go wot without a wideband

you need a wideband before you can judge anything
Besides a bad fuel and timing, the idea of an exhaust restriction (broken cat) is rather intriguing. He'd have limited power, but have no trouble making boost.
good2go is offline   Reply With Quote
Old 05-30-2016, 01:11 AM   #15
Senior Member
 
Join Date: Oct 2013
Location: NorthWest NJ
Posts: 948
Total Cats: 41
Default

Quote:
Originally Posted by good2go View Post
Besides a bad fuel and timing, the idea of an exhaust restriction (broken cat) is rather intriguing. He'd have limited power, but have no trouble making boost.
Our Volvo 240 did that with a cat once. It wore into a perfect sphere and would occasionally plug the exhaust. Would go from making... umm.. well, as much power as a 240 ever made, to making about half the power a Beatle makes, but otherwise run just like normal.
x_25 is offline   Reply With Quote
Old 05-30-2016, 04:10 AM   #16
Senior Member
iTrader: (2)
 
williams805's Avatar
 
Join Date: Oct 2013
Location: Goleta, Southern California
Posts: 502
Total Cats: 25
Default

Quote:
Originally Posted by good2go View Post
If the bypass is failing, but not dead, he can make boost, but probably not hold it reliably. Also, the synchronization of the dual TB's, as well as the off-throttle butterfly position on the SC TB can make a huge difference in "air noises" made both on and off throttle.

.02
Nope. The spring probably isn't dead. Which means boost is there. Also, he says 7psi. Tune is bunk. They said they checked, but I don't know what that means. Seen a few look at the spade connections and say "looks good". In reality, there was no connection.

if there is boost present in the intake, and you're not making more power than stock, your tune is bunk. Bad cards, or bad connection.
williams805 is offline   Reply With Quote
Old 05-30-2016, 05:35 AM   #17
Supporting Vendor
iTrader: (10)
 
Reverant's Avatar
 
Join Date: Jun 2006
Location: Athens, Greece
Posts: 5,396
Total Cats: 189
Default

If it feels/is faster at part throttle than at full throttle, it's running lean.
Reverant is online now   Reply With Quote
Old 05-30-2016, 09:01 AM   #18
Junior Member
Thread Starter
 
Join Date: Nov 2011
Location: Ottawa, Ontario, Canada
Posts: 105
Total Cats: -1
Default

Defenitely not the connections, he makes circuits for a living, everything was soldered and tested. Power cards could be bad, or the cat could also be bad, I like that bad cat idea, I'd never thought of that!

Car isn't missing, although I did feel some hesitation going through the revs slowly.

Plugs were black with soot, leading me to believe running rich.
Frenchmanremy is offline   Reply With Quote
Old 05-30-2016, 09:22 AM   #19
Elite Member
 
Join Date: Apr 2010
Location: Newcastle, Australia
Posts: 2,585
Total Cats: 21
Default

Quote:
Originally Posted by Frenchmanremy View Post

Plugs were black with soot, leading me to believe running rich.
yeah it ran rich at one point, but when?

get a wideband
nitrodann is offline   Reply With Quote
Old 05-30-2016, 10:45 AM   #20
Junior Member
Thread Starter
 
Join Date: Nov 2011
Location: Ottawa, Ontario, Canada
Posts: 105
Total Cats: -1
Default

Quote:
Originally Posted by nitrodann View Post
yeah it ran rich at one point, but when?

get a wideband
It will be installed this week.
Frenchmanremy is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Voodoo, ITB, 450cc, 325cc, T3/T04E, vlsd, 1.8 Throttle body mmmjesse Miata parts for sale/trade 8 08-21-2016 07:23 PM
Springs, NB Throttle body, NA 1.8 Test Pipe skipstr Miata parts for sale/trade 2 03-31-2016 10:35 PM
Miata Motor Murder Mystery! Elfering Engine Performance 11 03-16-2016 05:06 PM
Idle issues with new MS3 install jko MEGAsquirt 2 03-15-2016 02:05 PM
Fuel management Mohanad A Reda DIY Turbo Discussion 13 03-10-2016 02:25 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 02:12 PM.