supercharger issue

[dscotland]

maybe if I give some more details, you guys can help pinpoint the
issue. It's not a poor idle as in a rough idle, it's poor as in sometimes
it idles and sometimes it doesn't.

When I bought the car, at idle the revs would cycle from down low (500rpm?)
up to about 2000rpm. It would do this constantly going from high to low
every couple of seconds as if you were blipping the throttle. I didn't
worry about it because it didn't ever stall.

I then fitted an intercooler, and it seemed to make the problem
worse. Instead of the revs dropping down low and coming up again, the revs
would just die and the engine would stall. I took it to a workshop and
they adjusted something, this made the idle problem better for a while at
least, but then I noticed the car was running way rich and using more
gas.

The weird thing is, its not a constant problem. Sometimes it idles
perfectly flat and happy. But starting the engine from cold you have to
continuously blip the gas to stop from stalling. You can't even just apply
a constant throttle to warm it up, because even at say 30% constant
throttle the revs can still drop off quickly and it will die if you don't
squirt the gas again.

Thoughts??
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| glenn roberts | |
| <supasparky@yahoo.co.uk> | |
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| 28/08/2004 09:01 a.m. | lub.org.nz> |
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| MX5List<mx5list@mx5club| Subject|
| .org.nz> | Re: new |
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Could just be a faulty Air flow meter, the plugs on
them have been known to cause problems especially when
so close to the enginge block as with the JRSC.
I thought the fuel pressure should be 50psi at idle
only when you pulled off the vaccum line to the
adjustable regulator??? should normally be 40ish when
idling.??
If your running rich then youve probably fouled your
plugs resulting in poor idle. I beleive the correct
plug for JRSC cars is an NGK bkr6e.which is one step
cooler than a stock plug.(please correct me if any
info isnt correct
Also some after market fuel pumps around can actually
overpower the stock fuel pressure regulator due to
massive fuel flow and the idle fuel pressure would
shoot up around 50-to 55ps.
Once youve got it sorted get yourself a "BIPES TIMING
CONTROLLER" from the states. It allows timing
adjustment and has temperature compensation to prevent
detonation that can still occur even when the timing
has been backed of to 6*. theyre about US$200.

[Matt & Sarah Avery]

My car does exactly the same. I set the idle quite high (about 1500rpm)
which makes it behave a lot better. Running an extra vacuum line from
the inlet manifold to the intake (before the repositioned throttle) also
helped slightly (check out sebringmiata.com for the article I followed).
That Intercooler is going to cause you more problems than its worth.
I've been a member of the SSCOR (Sebring SuperCharged Owners Registry)
mailing list for a couple of years now and from what I have read, most
people give up on intercoolers on supercharged mx5's. The reason is that
the throttle is repositioned before the blower giving a much larger
"throttled volume" of air. When you add an intercooler (air to air is
what I'm guessing you fitted) this volume increases by a considerable
amount and causes problems. I have read reports about a dozen of these
cases on the SSCOR list and all of them report poor idling and a
sensation like bad "turbo lag".
Most people on the list who have money to play with (unlike myself-Boo Hoo)
Tend to go though the following stages:

1- fit standard supercharger kit
2- love it
3- need more. Fit different sized pulleys for more boost.
4- goes faster but detonates.
5- fit intercooler (usually water-to air type)
6- spend lots trying to tune out problems with driveability.
7- throw away intercooler and fit water injection.
8- spend lots more money on tuning and begin to get fed up with all the
little problems that occur with overdriving that poor little blower.
9a- Rip all of the "extras" off and go back to the standard kit and find
that although the power is less, the driveability is much better and so
is their enjoyment levels.
Or...
9b- fit an M62 blower or a "coldside" kit and go "power mad".

There is a member in Hamilton who has fitted a water-air intercooler
(pinched from a Legacy I think) to his supercharged 1800 car. It is also
running slightly higher boost, though he has fitted a Link ECU to tune
it better. Last time I spoke to him he seemed pretty pleased with it.

[Jeff]

When this happened to me it was because the Throttle Position Switch (TPS)
was slightly misadjusted - when things got hot the engine would lose the
"foot off the throttle" signal and bounce between the 2000rpm idle limiter
and the low idle limit. I had to loosen the screw and twist the sensor about
a zillionth of a mm to get it right, as per the Enthusiast's Manual. If you
have a Link ECU you can tell by looking for the "*" on the handcontroller.

But then I don't have a supercharger, so who knows what's happened to your
TPS !!! Maybe Fletch/Lou/Gary/Ray will know ...

[dscotland]

thanks for the detailed reply. I've found and joined that forum now too, so
may post a few queries. What's a coldside kit and M62 blower??

Does anybody know what sort of money a pair of standard MX5 seats may be
worth (out of an 89 NZ new)? Just sitting in my garage...

Duncan
|-----------------------------+-------------------------------------------|
| "Matt & Sarah Avery" | |
| <avery296@slingshot.co.nz>| |
| | To|
| Sent by: | "'MX5List'" |
| e-admin@mx5club.org.nz | <mx5list@mx5club.org.n|
| | z> |
| 02/09/2004 09:51 p.m. | cc|
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| Please respond to | Subject|
| MX5List<mx5list@mx5club| RE: supercharger issue|
| .org.nz> | |
| | |
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|-----------------------------+-------------------------------------------|


My car does exactly the same. I set the idle quite high (about 1500rpm)
which makes it behave a lot better. Running an extra vacuum line from
the inlet manifold to the intake (before the repositioned throttle) also
helped slightly (check out sebringmiata.com for the article I followed).
That Intercooler is going to cause you more problems than its worth.
I've been a member of the SSCOR (Sebring SuperCharged Owners Registry)
mailing list for a couple of years now and from what I have read, most
people give up on intercoolers on supercharged mx5's. The reason is that
the throttle is repositioned before the blower giving a much larger
"throttled volume" of air. When you add an intercooler (air to air is
what I'm guessing you fitted) this volume increases by a considerable
amount and causes problems. I have read reports about a dozen of these
cases on the SSCOR list and all of them report poor idling and a
sensation like bad "turbo lag".
Most people on the list who have money to play with (unlike myself-Boo
Hoo)
Tend to go though the following stages:

1- fit standard supercharger kit
2- love it
3- need more. Fit different sized pulleys for more boost.
4- goes faster but detonates.
5- fit intercooler (usually water-to air type)
6- spend lots trying to tune out problems with driveability.
7- throw away intercooler and fit water injection.
8- spend lots more money on tuning and begin to get fed up with all the
little problems that occur with overdriving that poor little blower.
9a- Rip all of the "extras" off and go back to the standard kit and find
that although the power is less, the driveability is much better and so
is their enjoyment levels.
Or...
9b- fit an M62 blower or a "coldside" kit and go "power mad".

There is a member in Hamilton who has fitted a water-air intercooler
(pinched from a Legacy I think) to his supercharged 1800 car. It is also
running slightly higher boost, though he has fitted a Link ECU to tune
it better. Last time I spoke to him he seemed pretty pleased with it.

[Matt & Sarah Avery]

The blower you have is an Eaton M48. An M62 is the next size up, which
can handle intercoolers apparently - check out BRPerformance.com for
their M62 Kits which Jackson Racing are now distributing. They also do
the Coldside kit (only for M1 1800cc cars though) which moves the blower
to the "Cold side" of the engine bay, sitting atop a CNC machined plate
which bolts directly to the engines intake ports (ie. does away with the
factory Intake manifold)

[Lou Girardin]

The JR unit is an M45. The coldside kit is the best set-up unless you want
more than 180 - 190 hp at the wheels. It gives response and general
driveability better than stock.
Don't bother with intercoolers on eatons, go for water/meth injection.
Lou

[dscotland]

Hi, a couple of things for sale.

pair of 1990 MX5 seats (offers wanted)
Set of standard minilite style rims, good condition but painted black
currently ($250)
Original NZ new stereo ($40)

reply by email or phone 027 2762 572.

Duncan