Duratec Header Temps
Page 1 of 2

Author:  a.moore [ January 27, 2013, 4:35 pm ]
Post subject:  Duratec Header Temps

Next time one of you guys with a Duratec powered car have it out, would you mind pointing a temp gun at each of the headers near the port while the engine is warming up and post what you see?

I've never paid attention to my temperatures before but I noticed today that the #4 cylinder is significantly lower than the rest. I'm trying to deduce if its normal due to the EGR port (mine is blanked at the valve BTW) or if I need to do a compression and leak down check.

Author:  Tongboy [ February 2, 2013, 9:33 pm ]
Post subject:  Re: Duratec Header Temps

a substantially different temp on a header pipe usually points to a down or misfiring cylinder - checking the plugs and comparing would be quicker than waiting on other's temps. EGR should affect all cylinders equally as it's pumped back into the intake - I can't imagine they would run a cylinder differenty to manage the output of that cylinder for EGR scavenging.

Author:  a.moore [ February 2, 2013, 10:58 pm ]
Post subject:  Re: Duratec Header Temps

That was my thought originally but the plugs all looked the same. :?

The weather has taken a turn for the worst so more testing is out of the question for the time being.

The Duratec taps into the #4 exhaust port for the EGR system and routes it through the back of the head to the external EGR valve. It then re-enters the head and is routed into the intake.

I currently have a blanking plate where the valve used to reside. On cylinders #1-3, the gas exits the head and goes directly into the primary but on the #4 there is also a large port that is tapped into the port. If I removed the EGR valve and the blanking plate was not there, exhaust gas from the #4 cylinder would leak out the back of the head.

I was curious if this extra mass of air in the #4 exhaust would cause the difference when the engine is cold and warming up while idling.

Author:  john hennessy [ February 3, 2013, 4:25 am ]
Post subject:  Re: Duratec Header Temps

is the blanking plate leaking and allowing air into the exhaust of #4?

i would measure mine but i have it wrapped all the way from the head,

are we talking 100 deg. or more?

are you running the variable intake system?

Author:  rx7locost [ February 3, 2013, 9:10 am ]
Post subject:  Re: Duratec Header Temps

Yep, what is "significantly" cooler?

What if you measured 12 inches from the flange. How do these temps compare there? It might be that the header itself just gets better conduction cooling to the head at the #4 position. I could see that #2 and #3 exhaust might run warmer just due to their physical proximity to #1 and #4. Can't explain why #4 doesn't match better.

Have you checked he accuracy of the 4 vac gauges you used to balance your TB's? Maybe #4 carb is not as open as the others. swap positions of the $ 4 gauge and see if it still shows a balanced condition. Or hold a piece of garden hose up to the front of each carb with your ear up to the other end so that you can hear the airflow. Do they all sound equal?

Author:  a.moore [ February 3, 2013, 6:04 pm ]
Post subject:  Re: Duratec Header Temps

john hennessy wrote:
is the blanking plate leaking and allowing air into the exhaust of #4?

Removing the EGR valve exposed 3 ports; exhaust gas into the valve, exhaust gas out of the valve, and a coolant port. My thoughts were that since it was not leaking coolant it was sealing. I guess I should recheck that.

john hennessy wrote:
are we talking 100 deg. or more?

The difference was between 100 and 200 degrees. If it was idling it was only 100 degrees but if I revved it a few times the difference went up to 200. I was out driving once after that I and didn't think to point a temp gun at the headers a few minutes after I turned the engine off. Once the snow stops and it warms up some, I'll do this test.

john hennessy wrote:
are you running the variable intake system?

No variable intake - just bike ITBs.

rx7locost wrote:
What if you measured 12 inches from the flange. How do these temps compare there?

The difference is similar.

rx7locost wrote:
Have you checked he accuracy of the 4 vac gauges you used to balance your TB's?

That is a really good point. I'll double check my settings and try moving gauges to different cylinders to see if it matters. I'll try your ear test and see if I notice anything. Fortunately with the way the GSXR throttle bodies are mounted, the idle stop adjusts the #4 cylinder and #1-3 are all adjusted relative to the #4. Raising the rest and not losing my balance should be pretty straight forward.

If no one reports this being normal, the EGR blanking plate is sealing, and the ITBs are pulling equally, I guess the next logical thing would be to perform a leak down/compression test. I had the ports sealed but I'm hoping nothing fell into that cylinder and did some damage. :?

Author:  rx7locost [ February 3, 2013, 6:40 pm ]
Post subject:  Re: Duratec Header Temps

Andrew, here is a scan of the Tuning S.U. Carbs Handbook showing the "approved' balancing method for dual carb setup. It might be a bit toughter discerning the differences in 4 bike TB's, but the process should transfer OK.

su tube.JPG
su tube.JPG [ 49.69 KiB | Viewed 5807 times ]

Author:  GonzoRacer [ February 4, 2013, 10:52 am ]
Post subject:  Re: Duratec Header Temps

+1 for the above method. I had better luck with it when I placed the opening of the tube (opposite the one stuck in my ear) at a 90 degree angle to the airflow into the carb throat. I don't see why it wouldn't work just fine for ITB's at idle.

JD "A Carb Named SU" Kemp

Author:  a.moore [ February 11, 2013, 3:13 pm ]
Post subject:  Re: Duratec Header Temps

I did what you suggested Chuck with a piece of hose; everything sounded about the same. I also put the gauges back on and compared; they were also showing good. Both methods agreed that the balance was pretty close so I scratched that off of the list.

Next I did a compression check* and everything was good on the #4 cylinder. Interestingly though the #2 cylinder was reading about 95 psi while the other three were in the 110-115 psi range. I'll have to keep an eye on it.

At that point I cleaned the plugs with the mapp gas torch and reinstalled them in their respective cylinders. When I reinstalled the coils, I switched the #3 and #4 ones to see if the problem followed the cylinder. Sure enough the #3 exhaust primary was now cold - bingo.

I pulled a spare coil from the parts box, installed it on the #3 cylinder, and low and behold all cylinders were about the same. The exhaust note also sounded less Harley and more Honda. I knew it didn't sound the same when I started it with the MS3x/ITBs but I wasn't sure if this was due to the intake change or what but apparently one cylinder not really doing much was to blame. What is odd though is the coil would fire in test mode in Tuner Studio. I guess maybe it didn't totally fail but something internally was going bad and causing a weak spark?

I have to question how long this coil has been like this. With the Focus ECU the engine's torque always fell flat at about 4,000 or 4,500 rpm and I could never tell if it was the factory cams, the stock ECU being in some sort of limp mode, or something else. I'll never know the truth but I have to wonder if this wasn't to blame. For comparison's sake, I never once had the back end step out in second gear with the stock ECU so something is getting better.

Thanks everyone for the help. Time to get back outside and take advantage of the 50 degree day. :cheers:

Author:  TooBusy [ February 11, 2013, 3:21 pm ]
Post subject:  Re: Duratec Header Temps

Buy one of these if you're running a multiple carb / TB setup. Best money you'll ever spend.


Author:  a.moore [ February 11, 2013, 10:09 pm ]
Post subject:  Re: Duratec Header Temps

Have you used one on ITBs? Would it only going on one cylinder at a time affect the accuracy?

a.moore wrote:
.....What is odd though is the coil would fire in test mode in Tuner Studio. I guess maybe it didn't totally fail but something internally was going bad and causing a weak spark?

I have to question how long this coil has been like this.....

Going back through my photos I just realized something - this coil was on the same channel as the igniter that fried a few weeks back. I'm fairly certain that I killed it. :BH:

Author:  rx7locost [ February 11, 2013, 10:34 pm ]
Post subject:  Re: Duratec Header Temps

Glad you got things figured out. :cheers:

Author:  TooBusy [ February 12, 2013, 9:08 am ]
Post subject:  Re: Duratec Header Temps

a.moore wrote:
Have you used one on ITBs? Would it only going on one cylinder at a time affect the accuracy?

I've used it on ITB's, a bank of Webers, a bank of Mikunis, and multiple pairs of Strombergs with great success.

The center section is adjustable so that you can get the venturi float close to mid range on one carb and use it as a reference. It doesn't cause a noticable restriction, just gives you a visual comparison of airflow.

The single hardest thing I've found on multiple carb setups is getting the butterflys to open at the same rate. Linkages and lash adjustments need to be spot on.

Once you get the adjustments dialed in visually you can use the flow meter to double check the results. I would clamp the throttle at about 2500 rpm and check the flow on each carb, then do it again at 4500 rpm.

What I learned was that multiple carbs were never fully in synch. I don't know if it was an intake issue or minor differences in the carb internals, but there were always differences.

Some intakes were better than others on flow consistency. The ones with balance tubes connecting the runners were generally the most consistent... They weren't the best performers. :?: Never could figure out exactly why

Author:  john hennessy [ February 12, 2013, 12:48 pm ]
Post subject:  Re: Duratec Header Temps

the need to balance carbs is because of pumping differences in each cylinder,on the example, the #4 cylinder was under performing due to an ignition fault, i would bet that when that cylinder was on the combustion stroke the cylinder that was on the intake stroke was also down a little on vacuum.

unless the cylinders are identical, the smoothness is noticeable if one cylinder is off. compression, ring blow by, valve seating, valve timing and valve lash can all affect what the cylinder is doing at idle because the quantity of fuel and air is very small in the cylinder, even differences in the stroke and rod length come into play, as you make the cylinders work, these differences become less of the total as the throttle opens so are less noticable, on an 8 cylinder engine, if you pull a plug lead off one cylinder, then go through the others, there is always one that also seems dead but not quite dead and you will find it's the one inducting when the dead cylinder is firing, this is due to a lack of fuel and air being sucked in so the combustion is shorter in that cylinder compaired to the working cylinders.

back in the day people lik Bob Lambeck would actually scribe the width of valve seats in addition to many other things to make sure every cylinder was pumping exactly the same, this was one of the secrets to speed the super stock guys used to maximise their performance.

if you look at some old pre war alfas and engines of that era, they would drive the cams from the middle of the engine to reduce the difference in cam timing due to crank and cam wind up.

many vw's with 1 ventury per cylinder can suffer these problems and if you put a listening tube down the intake of each cylinder you can actually here the difference in pull and the valve slaming shut.

if you add a vacuum balance pipe to the manifold the pull from the other cylinders compensates for the inaduquate cylinder, thus the engine seems smoother but it's just really a band aid on a poorly prepped motor with cylinder balance problems which can usually be atributed to stacking tollerances during assembly or combustion chamber size variations.

this is most noticable when you have to "stagger jet" the carbs due to unequallity in pumping efficiency, this i common on webbers and is evident in the transition circuit and air bleeds.

try this for fun, do a compression test with the throttle plates closed and see if they are all the same and if they take the same amount of cranking revolutions to get to their highest reading, then try with the throttle at wide open and see the difference, at wide open throttle the suction is easier on the engine so pumping differences are less and the compression comes up much quicker, if it doesn't then you have a problem!

i watched with interest the tv show where the guy from esslinger used a baffle in the intake to equal out the fue/air distributionl in the engine, i believe he was just blinding the good cylinders and dragging them down to the level of the bad ones, the middle two were bad and the additional length of the outside ones gave them a better pull so he used a U shaped baffle to screen the outside cylinders cutting the baffle untill they were all equal, this is a sign of a bad manifold design, just think what could have been achieved with a pair of webbers instead of a single holley.

a friend of mine own a sixties gasser, this car won indy so is a good example of injected gas small block, when the guy was racing the car, he would adjust the fuel distribution based on plug color to get the same mixture in each cylinder so that the bang was equal in each and the closer he got to equal the faster he went.

i also know someone who raced jaguars with tripple S U's he would thin the dashpot oil in the rear carb because it would run cooler than the front two, allowing the pistons to rise at the same rate to prevent a bogg comming out of a corner.

even more of my speed secrets going for free.

Author:  john hennessy [ February 12, 2013, 1:36 pm ]
Post subject:  Re: Duratec Header Temps

really the only way to quickly set the mixture cylinder to cylinder is based on cylinder KV, i have an old sun machine from the sixties, it would have shown the original fault in the coil instantly. because the KV would have been low on that cylinder compared to the others, if they were all low, then the mixture would be rich, if they were all high the mixture would be lean, finding the sweet spot is the science and averaging the cylinders to the maximum not stifling the good ones for the sake of the bad ones.

the guy who invented the SU carb was a genius because it adjusts the mixture according to air flow and adjusts the air flow to cylinder efficiency.

Page 1 of 2 All times are UTC - 5 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group