Red dot intake cam sprocket?

[Jphoenix13]

Getting set up to replace my cam belt and I discover my intake cam sprocket has a red dot. The exh sprocket is a blue dot.

 

What is the meaning of the red dot sprocket? A forum search yielded no results. There are no other dots on the sprocket.

 

I'm installing a JAE blue with new tensioner, v-belts and hoses.

 

When I bump the car forward to move the engine and line up the sprockets, I can see the old belt lift slightly on the intake cam sprocket as the slack is taken up downstream of the exhaust sprocket (belt pulling on the exhaust) and bunches up at the entry to the intake sprocket where the slack presents itself.

 

I guess it's a bit looser than it should be

 

TIA,

 

Jim

 

 

[Vulcan Grey]

Since you are looking from the back of the engine, the markings are actually backwards, which is how they are supposed to be.  If you were to look from the front of the engine, then the intake would be a blue dot and the exhaust cam would be a red dot.

 

These are put on the USA engines to slightly change the timing to pass emissions, that how Lotus sent them over.  The UK cars got green dot cams on both intake and exhaust.

 

You have a green dot cam on your oil pump, which you could move over to the intake cam for the originally intended timing and slightly better lower response.  Your oil pump timing does not matter on the S4.

 

Green is 104 MOP, Red is 110 MOP, and Blue is 100 MOP.

 

And yes, your belt does sound a little loose.  You'll have to tension the new belt using the acoustic frequency method. http://www.thelotusforums.com/forums/topic/56697-service-time-oil-filter-and-cambelt/?p=452399

[Jphoenix13]

Thanks Travis,

 

Having just climbed out from under the car, I can't even see the tensioner and can barely see the oil pump cam at this point. Looks like I'll need to remove the engine cover to get at the alternator with the car up in the air. This is going to be fun. (Edit - actually. I can just raise it up vertical I just realized - no need to remove it entirely)

 

How difficult is it to remove the green dot off the oil pump shaft?

 

Looking at the belt underneath, it is very - perhaps dangerously, loose. Glad I decided not to do that last track day last October. This belt has gone too long in my opinion.

 

I did read all of the tenioning posts and have Tune It app on my phone, so I think that's the easy part.

 

I'm glad this is my fun hobby, if I had to do this for a living, I'd be bitchin' and swearin'!

Edited January 11, 2014 by Jphoenix13

[Jphoenix13]

Travis, when you say the oil pump timing does not matter on the S4, is that because ignition timing is not taken off that shaft? So I need only be careful not to turn the shaft backwards because of the chargecooler impeller, no need to mark the oil pump pulley position?

Jim

[sailorbob]

UK cars had blue and red dot cam pulleys too, only the oil pump got a green dot pulley.

 

Ignition timing on the Delco ecu'd cars is controlled by the ignition module and ecu so there is no need to worry about the oil pump pulley position. Just do not turn it backwards because it can damage the chargecooler pump vanes.

[Jphoenix13]

Thanks Derek.

[Jphoenix13]

So on my S4, the crank timing marks are underneath the timing pickup probe, doesn't look like the book photos. Took a while to figure that out, also no pointer, so I guess the probe is the pointer? Looks dead on if it is.

[sailorbob]

The flywheel timing mark pointer should be just to the right of the crankshaft sensor when viewed from the rear.

[Jphoenix13]

OK, taking a lunch break. Old belt is off, pulleys swapped, now a green dot on the intake. Next is replacing the tensioner bearing, the old one is slightly rough, so that was a good idea. Car has about 43k miles on it. Then blue belt goes on followed by a fight with the v-belts. The power steering pump belt was a serious fight, finally gave up and cut it.

[Techspy]

Are you putting a green dot on the exhaust too? I just had my engine rebuilt (lost timing belt while driving) and put greens dots on. What a difference!

 

As for the power steering pump belt, I pulled the pulley off the power steering pump, put the belt on and re-attached the pulley. It was much easier for me that way.

[Jphoenix13]

No, I don't have another green dot. But next belt change I will put a green dot on the exhaust.

Great idea on the PS pump, Thanks! I broke my special Allen wrench tool trying to get the upper bolt out, truly pissed with that!

Just got back from Harbor Freight with a hydraulic press to press off and on the tensioner. That old bearing was quite rough.

Edited January 12, 2014 by Jphoenix13

[sailorbob]

  Do not flatten the timing belt like you have done in the photo, it can damage it.

[Jphoenix13]

The flywheel timing mark pointer should be just to the right of the crankshaft sensor when viewed from the rear.

Got it, it's so hidden by stuff I would never have found that tiny hole! Thanks for the heads up on bending the belt, like they say, first do no harm.

After buying a hydraulic press and replacing the tensioner bearing, the belt is on and tensioned using the acoustic freq meter method on the iPhone. Timing checked and good, but I marked the wrong side of the belt as shown in the photo above and now I'm well practiced at removing and replacing the belt without scratching it.

Time get get the rest go the bits back on.

[Jphoenix13]

Well, that was a serious job, but well worth it. I'm surprised how quiet the engine is now at idle. Some of the previous noise had to be that old tensioner bearing, but I think the old, loose belt was contributing some noise as well. Set the new belt to 103hz and I get just a bit of whine around 2800 and up, I expect it will quiet down as it beds in, I'll check tension again tomorrow after it's cooled down.

 

It seems to be a bit more responsive at lower speeds and idle is better, but still has the lovely lumpy Lotus idle. I think it tool me 30 minutes to get the radiator drain plug back in, between that plug and the alternator adjustment bolt, I probably lost an hour and a half of my life.

 

John, that was a great tip on the PS pump pulley,    I had to take it off anyway to get my hand on the coolant hose to get it coaxed back on. I read somewhere to position the clamp carefully on that hose to miss the belt and that was excellent advice!

 

So thanks for all of the tips, write-ups and hints guys, I could not have done this without them. I spent quite a bit of time on the iPad in the garage looking up threads and reading the manual.

 

Tomorrow night I'll check the cambelt tension again when it's cold, bleed the coolant system, check for leaks reinstall the belly pan and take it out for another spin. I'll be back driving the Lotus to work  by Tuesday  

 

[Jphoenix13]

It's interesting to note that with the rear jack stands located just forward of the rear jack points (on oak wood blocks) that there is very little weight on the forward jack stands. I can actually rattle those forward jack stands a bit, didn't try lifting it up, but it's good lesson in Lotus weight distribution.

 

 

Edited January 13, 2014 by Jphoenix13

[Techspy]

Good job! After my recent mis-fortune I will be replacing the belt myself more frequently so I am glad to hear that you got it done without posting the car for sale

 

I have that whine with the blue belt as well. I have about 475 miles on it (went for a 75 mile ride through the country roads today as it was such nice weather finally). At 1000 miles I am going to do an oil change, check all belts and address a trans leak (coming from the roll pin I believe). I don't think there are too many people running the blue belt yet so I am not sure what to expect for that whine and if it goes away eventually. I would like some input on whether or not people have had to re-adjust the blue belts tension and at what mileage. Maybe its too new?

[Mike6]

Personally I think its a bit of a no brainer not to replace the tensioner at every belt change. I think its mostly garages that dont change the tensioner. 

[Jphoenix13]

This afternoon, I checked the cambelt tension again because it still has a whine and found it to be 136hz in the correct position (cold engine). I re-read the book and many posts and read this post again by Esprit2 on the Lotus Talk Forum:

-- Tension:

The Lotus recommended tension gauges (the Borroughs and Clavis Frequency Meter) are sensitive to changes in the belt itself.

The Borroughs' reading changes with belt thickness and stiffness, and the blue HNBR belt is both thicker and stiffer.

Any taut strand's frequency response (guitar string or timing belt) varies with the strand's weight and stiffness, and the blue HNBR belt is stiffer and heavier (and the HTD is thicker and heavier than the trapezoidal).

Even if you use the Borroughs or Clavis according to Lotus' old procedures, they will not produce the same linear tension in the blue HNBR belt that Lotus originally intended when the specs were written.

In my limited experience with the blue HNBR belt, if you set the tension to 95 on the Borroughs gauge, the belt will run with a pronounced whine. A belt that whines is usually telling you it's too tight. IMHO, I prefer to set my black belts a bit on the tight side, and sometimes do hear a hint of a whine. But the blue belt at Borroughs 95 isn't hinting... it's whining. IMHO, that's too tight.

Backing the tension down until the blue belt no longer whines, gets it down to about Borroughs 80. Okay, maybe I'm an out of date dinosaur, but 80 tension in a 9XX belt just makes my skin crawl... IMHO it's too loose. I have no particular engineering insight to the HNBR belt, but I won't set one to Borroughs 80 on any 9XX engine I work on.

Borroughs 90 is the lowest tension Lotus ever recommended for an OEM black belt, and using that tension on a blue HNBR belt produces a slight whine... a whine that tends to fade with time as the belt beds in. Since my normal MO is to set the belt a wee bit tight anyway, I'm more comfortable with 90 and a hint of a whine than I am with either 80 or 95.

I have not yet set a blue belt to Borroughs 90 at TDC, and then taken a frequency reading at 30 BTDC, so I have nothing to offer those of you using a Clavis, or a frequency analyzer AP on your PC or smart phone. However, vibration theory dictates that 100-110 Hz on the blue belt will result in it being too tight/ whining. Just my thoughts. --

I only copied part of his post here and it's well worth reading the entire diatribe because I find it very well done. Here's a link: http://www.lotustalk.com/forums/f164/lets-talk-about-timing-belts-139314/index2.html#post2047921

So, I lifted the car up, got under and learned how to get wrenches on the cambelt tensioner nuts for about a half hour, then adjusted the tension. Got back up, checked it with my iPhone and no reading, zero hz. OK, so I learned something, that I forgot overnight; after adjusting the tensioner, I have to rotate the crank through 2 full revs of the engine, then take a reading and voila! I get 122hz. It was 103 last night before the test drive, so here we go.

I go back down under and get the wrenches back on the nuts (I'm getting good at it now) and rotate the engine 2 revs and climb back out and it's getting closer. 115hz now. Two more trips down under and I'm at 101 and that's good enough.

I drive the car, no whine. I park it and climb back under and no leaks, no interference with belts and hose clamps, etc, so I put the belly pan back on and that's it.

I lift the front and bleed the coolant system, top it off (added a bottle of Redline water wetter) and this job is done!

Damn that was much more difficult than I expected, but it's so much better. I could really feel that green dot pulley tonight, feels smoother at lower rpm's somehow, a bit more pickup from low dpeed and the engine idles quieter and kinda different. Now I need a green dot for the exhaust, then I can do the cambelt dance again

Edited January 14, 2014 by Jphoenix13

[sailorbob]

The tension setting frequency of a new HTD belt is 100 - 110 Hz when the engine is at a temperature of 15 - 25 deg C. Outside of this temperature range or using a different belt will mean a different frequency is required. What did JAE recommend?

[Jphoenix13]

The tension setting frequency of a new HTD belt is 100 - 110 Hz when the engine is at a temperature of 15 - 25 deg C. Outside of this temperature range or using a different belt will mean a different frequency is required. What did JAE recommend?

JAE said use same tension as the normal belt, in accordance with the specs in the Lotus manual.

[Techspy]

Good report. I am curious to see what my tension is when I check it next. I get that whine just over 2800rpm.

 

Oh, and just wait until you put the exhaust green dot on!

[Jphoenix13]

Drove the Lotus to work today, so nice! I may have exceeded the speed limit on the freeway once or twice :-)) and that's not easy to do in rush hour traffic on I-5, but at 4:55 am, there's one stretch of highway 18 that is hazard-free and that car just loves accelerating up the curving on-ramp and into a clear three lane stretch, slow down to 65 mph after a couple miles. Be still my beating heart ;-) then off 18 and in-line on I-5, still doing a reasonable 70 at times, no whine from the belt, so life's good.

Going to be a nice weekend here in the Puget Sound, so I'll be putting some miles on the car. Next project is to replace the lift struts on the engine hatch. That will be child's play after the cam belt!

Edited January 15, 2014 by Jphoenix13

[Techspy]

Cool!

 

FYI I replaced my struts with D4408 struts from Advance Auto. Work great and I was able to transfer the break light wire connections to the new struts. And they are cheap!

[Jphoenix13]

Good tip, thanks for that John.

[jonwat]

I'm not a fan of green but that looks stunning.