Fuel Economy cam updates

If you can run it hard before and after and take some boost-drive readings and note bottom end spool and top end power looking for differences
 
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WUnderwood, COMP461:)hehe:), DISTURBED*, Hamilton Cams*
 
Got the data for you. The turbo spools even faster. Very little throttle input is needed. Cruising EGT's are up about 50 deg. WOT, I tried....LOL it is still wet here from the rain and all it would do is spin at half throttle. I'll try again once it dries out. Truck also runs quiter and very very smooth.
 
crazy that 5tho is noticable. Zach what are the negitives to running tighter lash? (besides the obvious danger from burning a valve)
 
WOT the max boost is the same. 39 psi. EGT's are the same 1300. NO change there.
 
ahale2772 said:
crazy that 5tho is noticable. Zach what are the negitives to running tighter lash? (besides the obvious danger from burning a valve)
Click to expand...

There is no danger of burning a valve.
here is how the lash for the 12v and 24v changes the two exhaust profiles factoring for different rocker ratios. These are total open time numbers at the valve(.001")

208@.050" exhaust profile 12v @.020" 250 degrees
12v @.015" 252 degrees
24v @.020" 246 degrees
24v @.015" 256 degrees

210@.050" exhaust profile 12v @.020" 288 degrees
12v @.015" 305 degrees
24v @.020" 274 degrees
24v @.015" 293 degrees

to understand at what cam lift the valve lash is taken up you divide the lash by the rocker ratio, so 12v would be .020"/ 1.69 = .01183" or at .01183" lift multiplied by the rocker ratio the .020" would have been taken up.

For the 24v it is 1.37-1.38 intake or 1.375 for an average and 1.34 ehxaust ratio.

As you can see, the difference in lash can do quite a bit to add duration at the lower lifts. Now you are asking how this translates to better spool, the added open time by itself is no better at making power, but it opens the exhaust a little sooner, which spools the turbo a little sooner. Based on the information we have so far in Dyno testing, the 178-208 likes small turbos that spool with very little turbine energy. We got a huge bump in the lower rpm but in the higher rpm range(over 2500) we did not see that gain carry out.

The 178-208-106.5 @.020" exhaust lash will do best cruising at 2000rpm or less. I would like all of you to test it again @ .015" and do a test at 1900rpm and one at 2100 or whatever the test speed was previously.

Zach
 
I will redo my test after the first of the year. I don't go back to work until then. I will do my test at 69mph which would be 2100 rpms and this is the speed I got the best improvement. About 1 mpg.
 
Zach, Are you talking about the light turbine wheel of say a Garrett turbo. I wouldn't think the 71 turbine wheel I run isn't that light. Seems like my test just validates your results above.
 
There is no danger of burning a valve.
Click to expand...

at what point would burning a valve come in to play? Im assuming there is some point that not enought lash can hurt things... from thermal expantion and what not... Am I wrong?
 
Thought I got some great numbers the other day. Went to my parents, about 75 miles. Got 16.9 with a slight tail wind. I was stoked. Return trip neted my 11.5 with the wind in my face. Danged trainin' wheels sure kill aerodynamics. LOL
 
Waiting on a good warm day with no wind....LOL That's been a tough one these days.
 
Hmm, Then that proves what we were thinking, we are going to make another small change and then we will have others that need to be tested if you are interested.

Thank you very much for the information! Any chance of you trying .005" on the intake for a tank?


DB, Does this confirm your thoughts?
 
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So, do you want us to change the intake to .005". Would you like me to do this before I redo the mileage run?
 
Yes, I am up for another Cam change and would like to continue the testing to see what you can do. I am not one to give up easily.
 
Posting to get updates on the cam progress. I would definitely be interested in such a cam if it helps for turbo spoolup.
 
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