Yet another pulley question...

[Godless Commie]

OK, if you guys are sick of me starting new threads, please let me know..

My Miata is not a "Miata" per se.. It is an "MX-5". The European variety 1998 model NB.
I understand my 1.8 liter engine breathes and operates a bit different than its US counterparts. Has a more aggressive cam, '01 style headers, etc.
(interestingly enough, I looked under the hood of at least half a dozen "MX-5"s during a recent meet, and yes, all of them - ranging from a '90 all the way to a '99 - had the same type, the '01 type, headers in them. Not a single cast manifold in any of those random year models!)

Well, the gist of the matter is, I am only producing just a smidgen under 7 pounds of boost, and it pretty much stays the same from about 5000 rpm all the way to redline with 110/65 pulleys. Whp is 200 or so.
I have a TDR I/C, and E-Cool.
The same exact setup was generating 10.5 psi on an '01 US model. I do know that for sure.

Should I go to a larger pulley?
If I should, what pulley size would you recommend?

Thanks!

[tann3r]

What is your altitude? Do you have any boost leaks? Is your bypass fully closing? Are you running a cat?

Also have you moved your bypass signal over to the vacuum block? I had a tear in the diaphragm that was a small boost leak. I rerouted mine to the VDB and picked up about 1psi. New bypass is on he way and I think that will fix my tiny vacuum leak.

Those could cause the lower boost reading.

The larger cam for sure will cause you to see lower boost as you aregetting more flow through the motor. The intercooler will also cause a pressure drop.

What compresion ratio do you have? The 10:1 01+ motors will show more boost than the 9.5:1 99-00 motors.

I'll have to look back at my datalogs but I think my boost curve was pretty similar. I'll try to log some and post them up.

[Godless Commie]

What is your altitude?
Right at sea level.

Do you have any boost leaks?
No I checked a few times..

Is your bypass fully closing?
Yes. I checked both the bypass and the butterfly itself by removing the top of the blower.

Are you running a cat?
Yes. It is in good shape. (I would have higher boost numbers if the cat was blocked, anyway.)

Also have you moved your bypass signal over to the vacuum block?
I certainly did.

I had a tear in the diaphragm that was a small boost leak. I rerouted mine to the VDB and picked up about 1psi. New bypass is on he way and I think that will fix my tiny vacuum leak.
I can safely say I have a perfectly healthy bypass assembly.

Those could cause the lower boost reading.

The larger cam for sure will cause you to see lower boost as you are getting more flow through the motor.

The intercooler will also cause a pressure drop.
Yes. It is supposed to drop from 12 psi to 10.5 with the current pulley combination.

What compresion ratio do you have? The 10:1 01+ motors will show more boost than the 9.5:1 99-00 motors.
I have 10:1 compression, as well.

I'll have to look back at my datalogs but I think my boost curve was pretty similar. I'll try to log some and post them up.

Any other ideas?
What about the pulley question?

[tann3r]

Cam overlap could be too much. I can't think of anythng else that would lead to the low boost reading. Have you checked to see that your boost gauge is reading accurately?

For the pulley question, it depends on your power goals. I was just about to put a 120mm pulley for sale.

[Godless Commie]

Cam overlap could be too much. I can't think of anythng else that would lead to the low boost reading. Have you checked to see that your boost gauge is reading accurately?

For the pulley question, it depends on your power goals. I was just about to put a 120mm pulley for sale.

I/we have checked the boost both on the dyno and on the road using several gauges. The gauge I have installed in the eyeball vent agrees with them all.

120mm? Hmmm.. If you were to make a small box for it, I am sure it could find its way to my door..
How much would you like me to part with for that chunk o'metal?
(I was thinking more like a 350mm pulley.. Remember, it will be 17.6 tons!:) )

[jwalton]

I don't think that I ever saw 12psi before the intercooler. I know that I was getting more than 7psi afterwards though... This is all very strange to me. The thng that really gets me is that you're getting the right power levels for that pulley ratio. Weird.

[Tom @ Fast Forward]

Belt slip?

[Dr Evol]

Belt slip or boost leak, boost should rise proportionally to RPM.

[Godless Commie]

Belt does not slip as far as I can tell. No funny noises, no black dust, no residue. Belt tension is great, and I have a rather expensive belt (and a spare) that I have measured meticulousy before I purchased them.

As for boost leaks, I use MONSTER clamps worthy of the space shuttle itself!
I also removed and resealed:
a) Top of the blower
b) The intake manifold
c) The dummy throttle body.

I used black silicone on both sides of the gaskets.

Also, I checked all over the engine for leaks using the carb cleaner and wideband monitoring technique I have described in another thread.

Suffice to say I am satisfied that there are no boost leaks to atmosphere. All air is finding its way into the combustion chambers.

The kicker is, I am generating the power levels I am supposed to with this setup despite the low boost numbers.
Is this a case of "more flow, less boost"?

Let's see what happens if/when I install the 120mm pulley.

[Tom @ Fast Forward]

Timing belt.

[Godless Commie]

Hmm. I had the timing belt replaced about 30-35K miles or so.
I watched the guy align the marks, so I am fairly confident the belt is not off.
Besides, I have driven the car before and after the timing belt R&R, there would have been a difference.
I have test driven, ran a few engines with the timing belt off a tooth. I am familiar with the funny vibrations, interesting Co and HC values, etc.
My engine displays none of the symptoms.

I will pull the fron cover and check just to make sure when I get into the engine next week..

[Godless Commie]

Just a quick thought..

Jim has a 10:1 engine.
I have 9.5:1 compression.

Would the lower compression, coupled with the more aggressive cam lead to the lower boost values?

(I wish the belt was slipping. Would be sooo easy to fix..)

[Tom @ Fast Forward]

CR has very little to do with boost.

[FormerDatsun510Man]

CR doesn't affect how much boost you have in the intake manifold. CR however is one of the things that determines how much boost you can safely run before detonation occurs. For example, if at 10:1 you can run 10psi before detonation problems start occurring, then perhaps around 13 or 14psi could be run with 9:1 CR. In the case of a supercharger, that would require to a pulley change to take advantage of the lower CR. However, changing the CR won't change what boost you see if no pulley change is made. What is the optimum CR? Depends on the setup. Really the best way would be exhaustive dyno testing with different pulleys and CR. We've seen that 9:1 seems to work the best for high powered MP62. I could see perhaps a really max powered setup may do best at 8.5:1... you know, 8000rpm, 20psi, etc.

Simply put, you lose power with lowered CR, but you gain back more with the allowable boost you can run... up to a point. That point is when you are running so much boost that you are going well out of the efficiency area of the supercharger (or turbo).

Bill

[Tom @ Fast Forward]

It's not quite so cut and dried as Bill put the numbers. Amount of power vs boost is directly proportional to the octane of the fuel as well. We run the 10:1 Miata engines (01-05) at 10.5 PSI all day every day without knock on 91 octane. I'm sure they would also run higher boost on better gas/octane.

[Godless Commie]

I have a feeling I know what's going on with my lower than expected boost:

When I pulled the blower to wrap my headers today, I saw a considerable amount of belt dust at the bottom of the blower..
And I had a flash about why boost was not rising, and remaining at almost 7 psi from about 4500-5000rpm on..
I mean, I had looked pretty hard to check for belt dust before... It just happens to be in a spot where you can not see it unless you remove the blower.

I promptly replaced the belt with a new one that I carry in the trunk.

Now,

Back to Jim Walton's car for a sec..
Jim told me on a couple of occasions that he used to see 10 to 10.5 psi.
I have the same exact pulleys he is using. Everything I have came from his car. (Thanks again, Jim..)
The only different component is the belt itself..
It's a 6K1094, meaning it's 1094mm, which is 43,07 inches..
Is this the correct size for a 110/65 setup?

(I noticed the auto tensioner could be moved in, further tighening the belt once it sets in - with the engine off of course.)

On a second note, I should be receiving my 130mm pulley soon.
What should I use for a belt on that pulley? (Brand, size please...)

Thanks a lot.

(Now I am reeeally scared about what will happen with a non slipping belt and a 130mm pulley... )

[Tom @ Fast Forward]

As long as the tensioner is between the limit lines, the belt should not slip.

[Godless Commie]

I do not have those marks on the tensioner, Tom.
My tensioner is absolutely perpendicular to the ground with my belt.
Tom, do you remember if Jim Walton had an FFS cut blower pulley?
It's an 65 mm, but the groove ridges seem sharp to me. (or, I am just being paranoid..)

Maybe I can do my own gatorback design on the pulley ridges..

[Tom @ Fast Forward]

Post a picture of your tensioner setup.

[Godless Commie]

Here are the pics..

Framing a decent shot is not easy in the dark, so please forgive the picture quality.

The narrowest point between the two belt halves (where the tape measure is) less than one inch, btw.

I took pics from different angles to be a bit more descriptive.

[Tom @ Fast Forward]

Ah. Not my tensioner. That belt looks to be too long. Way too long.

[Godless Commie]

Thank you!
I am so relieved..
Nothing like finding the real reason behind a problem (even though one could miss it entirely while, the whole time, the culprit has been staring him in the eye)

So, what belt should I use with the 130/65 combo on my hotside?

[Tom @ Fast Forward]

You have a 110/65 now, correct?

Can you read the belt for a number like 060435?

[Godless Commie]

Sorry Tom..
It's all metric over here. The belt says 6PK1094, which is 43.07"..

And yes, I do have a 110/65 right now.

[Godless Commie]

6PK1094 translates to a K060431.
That's what Jim had told me. I just dug into my older emails with Jim.

[FormerDatsun510Man]

With the 130/65 pulley setup on my Hotside I ran a Gates 60441 belt, which means 44.1". The last three digits means the belt length in inches. The belt designation you describe is the same number except in mm rather than inches. Simply multiply the inches by 25.4 and you get the mm. So for a 60441 belt, the metric equivalent would be 6PK1120 (1120mm = 44.1")

Bill

[Godless Commie]

Thank you Bill..

So, 1120 it is.
By applying Tom's formula - I remember reading it takes a 8 mm in belt length for every 5 mm difference in pulley size, I reach at:

1120 - {[(130 -110) / 5] x 8]} = 1056
where,
1120 is the proper length of a belt for a 130 mm pulley,
130 and 110 are the pulley sizes, respectively,
5 is the pulley size increment, in mm,
8 is the difference in belt length per 5 mm in pulley size difference, in mm.


1120 - 64 = 1056 (length for a 110 mm pulley in mm)

1056 / 25.4 = 41.57 (same length in inches)

So, My current belt with the 110/65 setup should be 41.57", 1056 mm.

I have a 1094 mm (43.07"), so, yes, it is too long..

By almost 38 mm (1.5")...

Jim, I hope you are reading this... :yes:
(just kidding)

[Satisaii]

Are you going to try a shorter belt with your current pulley to see if it has been slipping?

[Godless Commie]

That's exactly what I was debating myself..

I should be receiving the 130 mm in a day or two.. I will just go and get a couple of 6PK1120 belts (one for the s/c, one in the trunk).

It's just that I do not want to go through the whole tuning thing just for a couple days..

On the other hand, it would be nice to see what the car is really capable of with the 110/65.

I honestly don't know.

EDIT:
I should at least try it.

[FormerDatsun510Man]

I get a different result from you for the 110mm pulley.

1120 - ((130 -110) / 5) x 8)
1120 - ((20 / 5) x 8)
1120 - (4 x 8)
1120 - 32 = 1088 (42.8")

So your current 1094 may only be slightly too long by 6mm (1/4"). On the other hand, there is generally enough takeup in the autotensioner to make up for this. You have the correct length belt if:

1) When the belt is new you should barely be able to squeeze it onto the pulleys by hand. This is a rough rule of thumb. I have had belts that required me to use an open end wrench on the end of the SC nose pulley to help it on... basically a 1/2 a size on the tight side, but I rather a tad tight than a tad loose. Once the belt is broken in, I have found it will go on by hand 99% of the time.

2) On the autotenionser you have three marks. The autotensioner should end up on the middle mark with the proper size belt in there. Note, that the FFS autotensioner is adjustable in addition to having the proper belt length to get the marks to line up correctly. See the attached pic. If it lines up on the mark on the left (green), the belt is too loose. If it lines up on the mark on the right (red), it is on the tight side (but this happens with a new belt). If it lines up with the center mark (blue), it is just right once the belt has been broken in.

Bill

[Tom @ Fast Forward]

I checked the customs tracking number. It is in Finland and out for delivery. You should have it tomorrow.

[Godless Commie]

I am gonna end up moving there, Tom..

Would you care to build a coldside for a snowmachine?

[Godless Commie]

I get a different result from you for the 110mm pulley.

1120 - ((130 -110) / 5) x 8)
1120 - ((20 / 5) x 8)
1120 - (4 x 8)
1120 - 32 = 1088 (42.8")

So your current 1094 may only be slightly too long by 6mm (1/4"). On the other hand, there is generally enough takeup in the autotensioner to make up for this.

Bill

That's what happens when I try to do math and watch a movie at the same time... :dupe:

[Tom @ Fast Forward]

We are working on stuffing one in a Ginetta G20 at the moment. If it fits in there, anything is possible.

[Tom @ Fast Forward]

Keep in mind that it is not my tensioner and is not mounted the same as mine and may not have the same spread of coverage.

[Godless Commie]

In light of what you and Bill have said so far, I will get a bunch of belts, and try them on before I buy them..

They let you try shoes on before you buy them, after all.. And they are more expensive then belts, anyway..

I can also re-spring the tensioner, too.. (and if that does not work, spring for a new tensioner) ;)

[jwalton]

Yeah, I just caught up with this thread as I've been upside down in my engine bay for the past 4 days finishing up my install. I choose to go with Bill's comments about the belt only being about 1/4" too long. :)

The SC nose pulley is one of Tom's. Actually, Tom put it on himself in his very own driveway.

[Godless Commie]

One should take pics and post them during an install, Jim..

I hope all's well with you and your projects.

Maybe there is a difference between your '01 block and my '98 in terms of the distance between the center of the crankshaft and the lower exhaust manifold studs.
One is the reference point for the belt, the studs are where the blower mounts.

[Godless Commie]

Wait....
The plot thickens:

I just received an email from FM saying that the belt I am using is spot on, and that I should be looking for a problem elsewhere..
They also list far longer belts than what we have come up with here for the 130 pulley.

Hoping that I shall not break any rules and offend anyone, I am pasting the body of the email I received below:

"That's the recommended belt, and your gap looks appropriate, so I'd be surprised if that was your problem. I'd look more towards mis-alignment of the blower or an old belt. To check the alignment, stand at the left side of the car and look across the crank pulley and nose pulley. They should be perfectly lined up fore-aft. If they're not, you'll need to loosen the bolts that hold the supercharger onto the HBA and slide it until it does line up.

We don't have a recommended belt size for a 130mm pulley, but a 126mm should use a K060441 (1135mm) and the 135mm should use a K060445 (1150mm).

I hope this helps, let me know if there's anything else I can do for you."

Like the song says.. where do we go from here?

:)

[Tom @ Fast Forward]

"Where do we go from here?"

Coldside :-)

[Godless Commie]

I bought a new belt for the 110 mm pulley today..

I went as small as possible and got one that is 1085 mm in length. It was a bear to put it on, but I have my tricks..
(Top pulley first, a quarter of the load side on the crank pulley, next. Car in 5th gear, keys in the pocket. Hold the belt in position with one hand, pull the car forward a few inches at a time. Slips right on te pulley.)

Anyway, this one is a rather thick belt with considerably softer rubber.
Does not slip.

I still cannot get more than 6.5 to 7 psi..

As soon as the revs go past 2000 rpm, the boost shoots to 6 psi.
Then it just sits there all the way to redline.

I'll go nuts..

First supercharged Miata with "fixed" boost..

[Steve in VC]

I bought a new belt for the 110 mm pulley today..

I went as small as possible and got one that is 1085 mm in length. It was a bear to put it on, but I have my tricks..
(Top pulley first, a quarter of the load side on the crank pulley, next. Car in 5th gear, keys in the pocket. Hold the belt in position with one hand, pull the car forward a few inches at a time. Slips right on Te pulley.)

Anyway, this one is a rather thick belt with considerably softer rubber.
Does not slip.

I still cannot get more than 6.5 to 7 psi..

As soon as the revs go past 2000 rpm, the boost shoots to 6 psi.
Then it just sits there all the way to red line.

I'll go nuts..

First supercharged Miata with "fixed" boost..Tom has tried to find a way to hit 15lbs at 2000RPM, and fix that to red line, if we can figure this out, maybe he has his approach.

I assume the pulleys are 110 / 65, so you should have 10+PSI at red line even with an engine that breathes really well.

Silly question, have you tried another boost gauge? Where is the gauge getting the boost from?

Do you have a wideband A/F meter? What does it read?

What engine management are you using? You aren't getting detonation, so the fuel it is applying is appropriate for the boost.

Have you been on the dyno? If not, on a flat road, how long does it take to accelerate from 40MPH to 70MPH in high gear (5 speed or 6 speed?) In 3rd gear in a 5 speed, 4th in a 6 speed?

Do you have an inter-cooler?

Have you sprayed a thin coating of dish soap on anything with boost, blipped the throttle and looked for bubbles?

[Satisaii]

Did you ever post a dyno plot?

[Satisaii]

You also asked what the problem was with my car. Even though this solution has yet to be verified on the dyno, we found that my exhaust valves were shimmed too tight. Mike could not get the minimum feeler gauge between the cam and the shim. Which would lead to the valves opening early, closing late, etc.

[Godless Commie]

I SMOKED MY CAR TODAY!!

I mean it. Literally.
Met with a friend who owns a small factory manufacturing galvanized bucket handles. The place was closed, and we had the place to ourselves. So, we tackled the "smoke machine" idea I had been toying for some time..

We used a portable 12V tire compressor, an insulated 12V water heater/insulated mug (pretty decent size, has a built in heater in the base to boil water for instant coffee or tea - less than 7 bucks..) some clear tubing, a couple of nipples and clamps, and baby oil.
No babies were harmed. The oil was purchased from a store.

The insulated water heater's lid is drilled in two spots, barbed nipples are secured with washers, nuts and plenty of silicone, hose from the compressor is hooked up to one nipple, clear tubing is hooked up to the other one.
Baby oil in the heater smokes very well after a few minutes, you start the compressor (unregulated air - takes a while to build up about 2.5 psi). The air intake just aft of the air filter is nicely blocked with four layers of plastic sheets and a clamp, brake booster hose is disconnected from the intake manifold, the clear tubing from the baby oil heater is hooked up to that port, and the waiting game begins to build pressure and smoke in the engine.

Lo and behold, we discovered SIX different leaks.. Four of them were from the I/C piping silicone hose clamps, one from the FPR vacuum line, and a small one from the EGR. I mean, I had installed those monster clamps on those hoses!
I checked inside the car, the boost gauge, and the boost lines to the cards, as well.

Anyway, took a while, but we fixed five out of the six leaks. I decided to just live with the EGR leak for now. I'll try and fix that some other day. (Ran out of time it was midnight by the time were done.)
Then we hooked up just the compressor to the brake booster nipple on the intake manifold. Again, we pumped about 2.5-3 psi in the engine and checked all the suspected areas with lots of soap water. All was well (except for the EGR).

On the way back, I floored the pedal on the highway. I am pretty sure I saw 8+psi on the boost gauge. Could have been more, but it gets to be really fast when you approach redline, and there was traffic.
I can safely say, no, my butt dyno says, the car is faster.

All in all, I spent an entire day building a contraption I thought would be helpful, and it worked like a charm.
I will hook up a second boost gauge and retest eveything to make sure when I get a chance.

Things are definitely looking up :)

[Steve in VC]

TV and this, you are having a good day.

Thanks for the instructions on the smoker.

[Tom @ Fast Forward]

I might have to build one of those smokers just to have around.

[FormerDatsun510Man]

I'm really glad to hear this! Just wait when you get that 130 pulley and see 13psi!

Bill

[Godless Commie]

Tom, you know, you do live in the states..
I'm sure you could fnd a used or refurbished unit, complete with all he adapters for next to nothing there..
As far as I know, the large ones are around $2000, and the small machines go for about 300 to 400 bucks, brand new..

I bet you could get one for about $100 if you looked around.

It's just that no one konw what they are over here.
I built mine out of desperation.

[Godless Commie]

BTW, has anyone experienced boost leak at the EGR valve before?

I might have to pull it and decarbonize the large pintle to assure a good seat.
What do you think?

[FormerDatsun510Man]

I can't say I have experienced a boost leak at the EGR, but then again I never checked with a smoke machine like you. One thing I can say is the boost I have seen on various setups, when running right, seems to be consistent. So, either they are all leaking a little bit like that and it is normal or they aren't leaking at all. I never looked that deeply into the EGR to be honest though. I guess the real tell tale would be on the dyno to cap off the EGR so no air can come out and then do runs with it hooked up (and leaking) normally. I would be curious if it makes a difference.

Bill

[Godless Commie]

I would be very curious to see results about the EGR valves on different Miatas, Bill.
Having said that, I have seen quite a few EGR valves pulled from V6 and V8 engines, and they were pretty much all coked up. Granted, they are lower revving engines compared to ours and more prone to carbon build up, but mine is ten years old and has almost 100K on it.
I am pretty sure I can pull the thing and give it a thorough cleaning to free up the pintle.
Then again, if I just cap the EGR ports and leave the valve in the car so it is still plugged in (and useless), do you think I would throw an EGR code?
I know OBDII systems do in fact throw a code, but please bear in mind that mine, while it is officially an NB, has an OBDI engine management system.

..........

Come to think of it, I could be losing boost two ways:
* to the atmosphere through the leak I have spotted, and
* to the exhaust system, through the not fully closing pintle.. (I do realize an EGR valve would feed exhaust gases to the intake under NA conditions. But, given the charge - pressure in the intake manifold, the charge would overcome the pressure of the exhaust gases, and force its way into the headers.)

Those valves are expensive little things. I'd rather cap it off and spend that money on the new Boundary ignition system. :)

[Godless Commie]

My 130mm has just arrived! (Thanks, Tom)

We'll see what happens.. ;)

(I need to deal with the EGR leak first, of course..)