| Author | Message | ||
| Jerry Covin (Pilgrim) (66.82.9.15)
Rating: N/A |
Just completed maiden voyage in '61 GMC TDH 5301, V692 TA engine, V730 Allison transmission, Lake County to Reno and back using I 80 at the pass. Need some help to maximize engine performance mechanically. Would like to improve both climbing ability and take off. Any ideas? | ||
| Henry R. Bergman, Jr. (Henryofcj) (67.136.241.239)
Rating: N/A |
I understand. Right now my Crown is a real SLUG on the grades. The Detroit 6V92TA does respond well to some modifications. The question is would such mods really help for the $money$ spent. Sure you can change the turbo, go to a larger intercooler and change out the injectors to N100 or type, open up the intake and exhaust sytems, larger air cleaner, etc., but it may cost $thousands$. Then....you have the question of the tranny living with all that power. Can the V730 handle 400+ hp with over 1200 pounds of torque? Even for a little while? Increased tranny cooling would also have to be addressed. The bottom line is that most anything is possible, the only question is...is it practical? Maybe the effort in this case could be reapplied in other areas of the coach. In the meantime, just crawl along like the rest of us.  | ||
| CoryDane RTSII (66.155.188.28) Rating: N/A |
Hey Henry, or any others.... I listened to a seminar the other day where they were talking about upping the jets or injectors in an engine. There seems to be a consensus that changing the jets/injectors does not really improve power because you are not increasing the amount of air that is getting into the cylinder to burn. You are only burning more fuel. The feeling of more power is perceived because of the additional fuel added when the throttle is opened but after the fuel ratio is maxed, the engine just exhausts the excess fuel that there was no air to burn. This was an engine guy from GM and he seemed to know his stuff. Does this sound right? "Imagine" cd | ||
| darisb (209.67.181.129) Rating: N/A |
Makes sense to me. I've been thinking about replacing my N65's with N60's for about a year now. Thanks for the input Cory. Daris | ||
| Jim Stacy (209.247.222.87)
Rating: N/A |
"The Book" has a chart showing what injector size COMBINED with what turbo gives what HP. The 6V92TA's are all the same internally. All have advcanced timing. Factory recommended changes for HP from 260 to 350 only require a turbo change for more air and an injector change for more fuel. If I remember correctly, the 350 HP was 90G injectors with a turbo with R/A ratio near 1. With more fuel comes more heat. As Don Mathews used to say "You'll get a fire going back there you can't put out." FWIW Jim Stacy | ||
| BrianMCI96A3 (65.40.116.190) Rating: N/A |
As an old school nascar guy once told me, "The limiting factor in how much horsepower you can get from any engine is how well it breathes." Still true and always will be. Brian | ||
| Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A |
Daris, there's usually a valve timing change that goes with a change from C60 to N65 injectors. I would look for a timing change going the other way, too. One of the best benefits of the C60/standard timing setups was the broad power band. You can go from under 1200 to 2100 RPM with a full throttle and a fairly flat torque curve. Peak torque is 1200 and peak horsepower is around 1650 RPM. With the N65/advanced timing setup, you are looking at peak torque at 1600 and a peak horsepower in the 1900 to 2100 RPM range. And I would be afraid to use a full throttle much below 1500 RPM. You're only looking at a gain of about 35 hp, so in many cases, I think that what you give up would be more than you gain. Certainly, that broad power band makes driving a standard shift much simpler. At least that's the way it seems to me. Tom Caffrey PD4106-2576 Suncatcher | ||
| FAST FRED (4.245.191.230) Rating: N/A |
"Daris, there's usually a valve timing change that goes with a change from C60 to N65 injectors. I would look for a timing change going the other way, too." On my boats 6-71 I removed HN 90 injectors with advanced timing and installed HN 60's. The DD dealer claimed I would not have to retime the engine , and so far (500) hours there does not seem to be a problem.3 oil samples so far. I wouldn't worry reinstalling the recomended N60's , as the engine MAY not have advanced timing from the N65 instalation. FAST FRED | ||
| John that newguy (199.232.240.225) Rating: N/A |
Isn't a 6-71 a whole lot different than a 6v92ta? There's no turbo to wait for when dumping all that extra fuel into that larger cylinder, is there? Or am I cornfuseled? I have a 6v92t that smokes terribly -on acceleration only-. It had larger injectors installed and apparently neither the timing was reset, of any resetting of, or installation of, a throttle delay was made. Had all that been done, I would need the rack reset to go back to the smaller injectors....... or so DD claims. | ||
| Doug (69.244.108.42) Rating: N/A |
Add propane injection...acts a s a fuel catalyst for better burn | ||
| John that newguy (199.232.240.225) Rating: N/A |
I'm not too sure who you posted that comment to, Doug. I'm not the one seeking info regarding the rack reset; I already asked and received my answer from the manufacturer and several well experienced DD mechanics. The propane injection stuff has been debated heavily here as long as I've been reading here. Most opinions suggest that it was not designed for two cycle engines. I am also of that opinion for all the reasons those more learned than I had pointed out in previous threads. The same sources I had asked about my acceleration smoke problem, also commented on the use of any propane injection. They too, were against it. | ||
| John Rigby (65.112.227.94)
Rating: N/A |
Tom Caffery, Do you have any info on N70,s and advanced timing I am running in my 671/4104.I missed meeting you in Salem. Thanks John | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
I have a some friends that have tried Propane, the only problem is that anything that ups horsepower, ups heat. I'm right on the bubble for cooling, so I'm holding off on propane for now... gary | ||
| Johnny (63.186.169.192) Rating: N/A |
"I listened to a seminar the other day where they were talking about upping the jets or injectors in an engine. There seems to be a consensus that changing the jets/injectors does not really improve power because you are not increasing the amount of air that is getting into the cylinder to burn. You are only burning more fuel. The feeling of more power is perceived because of the additional fuel added when the throttle is opened but after the fuel ratio is maxed, the engine just exhausts the excess fuel that there was no air to burn. This was an engine guy from GM and he seemed to know his stuff. Does this sound right?" Yes...IF AND ONLY IF the engine is already getting enough fuel to use all the air it's getting. For example, I'd bet the derated 6V71 at work could get bigger injectors (somebody rebuilt it with 55's) & have a sizable power boost with no other changes. I know a 1989 Cummins 6BT in a Dodge pickup can get 225HP injectors (stock is 165HP) with no other changes & realize an ENORMOUS power boost. Jerry: how crud-filled is the intercooler? If it's clodgged, it works like a clogged radiator: not much cooling. Worth a look. | ||
| darisb (209.67.181.129) Rating: N/A |
Tom, I think you're right. My bus came with N65's. I didn't find out until after the in-frame was done that the mechanice put a new set of N65's in it. I suspect that my motor is at standard timing. I've been told that you have to remove the transmission to change the timing. With everything elese that still needs to be done, it seemed expensive at the time. After a couple long trips, I've decided I'm more interested in the extra 1 or 2 MPG, rather than an extra five MPH on the hills. You're right about half throttle. My engine has less than 10k on it, new heads, new injectors, clean screen over the blower, regularly serviced air cleaners. Anything over half throttle and I start getting black smoke on acceleration. It runs great on the highways and climbs most hills at 1700 in third. My local mechanic always complains about the smoke. I think he floors the throttle when he's test driving it. I don't notice too much, but then I'm not hot rodding it around town either. Regards, Daris | ||
| John Rigby (65.112.227.94)
Rating: N/A |
Daris, What speed is 1700 rpm in third gear?? John | ||
| darisb (209.67.181.129) Rating: N/A |
I forget. It's been a while, since I've done any hill climbing. Thinking it's something like 40 or 45. Two years ago, when I took a 5,000 mile trip, RJ Long advised keeping the RPM range between 1,600 and 1,700 when climbing hills to keep the heat down. Worked like a charm. Engine stayed in the 195 degree range and no black smoke. Daris | ||
| John Rigby (24.174.238.253)
Rating: N/A |
Daris Thanks. R.J. makes a great point with the rpm range being between 1600 and 1700rpm when climbing. I have in the past 18 years blown two head gaskets. During both these experiences I did not have a tack. I do now and will keep to R.J,s advise. Thank you again Daris. John | ||
| Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A |
John, I don't have the tables that show what should be used. I would think that Geoff would be a good source of info. I have noticed that a lot of people with 6-71N setups use N65 or larger injectors. I wouldn't think that they would get the most out of them unless they were timed for it. Most of the time, the discussions about injector sizes and timing have not mentioned the effect of two or four valve heads and it seems to me that all three items are going to have a bearing on economy, smoke and power. I can only imagine the combinations that you can get into when turbos are added into the mix. I wonder if anyone can clear up whether 4106s originally had two valve heads and if that was a reason that they were governed to 1650 RPM. What led Detroit Diesel to kick up the governed RPM to 2100? Was it always that high? Sorry I didn't have more information for you, John. Tom Caffrey PD4106-2576 Suncatcher | ||
| John Rigby (24.174.238.253)
Rating: N/A |
No problem TOM. My 671 has a) Two valve head B) N-70,S C) Advanced timing. I can make it lug, at low rpm, but it will NOT SMOKE, No matter what I do with it. Except of course overheat. I know I have helped the problem with my new Rad core and what I have learned from Daris and R.J. I would add my 671 seems to have very good power and alough I do change down on the steep hills and mountains, the past loss of power has been in direct relasonship to the raise in engine temperature. Hopfully per above this has been corrected. John | ||
| Jim-Bob (205.188.116.136) Rating: N/A |
The reason the 4104's inline 6-71 doesn't smoke is the "Fuel Modulating Governor" which seems unique to the 4104. This governor overrides the driver's foot in that you can floor it and the governor has a soft spring link that gives & allows the governor to bring the speed up slowly. The book calls for much larger injectors (as big as 80s) than are common for later engines but it has an extra spring in it that only allows full rack below a specified RPM. (Like when you lose RPMs going up a medium hill) I currently have N65s in mine with standard timing and it just does NOT smoke other than a tiny grey puff when I shift. IF YOU DRIVE AT THE SAME SPEED, you will not save fuel by going to smaller injectors nor will you burn more by using the largest size specified for your engine. Injectors are not just hollow tubes like jets that allow x amount of gas to flow through regardless of need. They are little adjustable output pumps that add just enough fuel to satisfy the governor. (The number reflects the injector's maximum calibrated delivery per stroke.) For example, your bus may need 55CCs per injector stroke to cruise at 60 mph at 1800 or so. The engine will get a perfectly metered 55CCs from either an N60 or an N80 injector. The larger injector will cause the engine to run the same speed with a lower percentage of full throttle. But you WILL lose hill climbing power by going to tiny injectors. At that time, the engine, climbing in third at 2150 rpms may need 70CCs to make full HP but your 60s reduce max power output. Result: The engine loses RPMs & you end up in second gear at 30MPH. I just changed to 65s from 60s. I notice that now I go up hills a lot better. My cruise used to lose 5-7 mph going over Interstate overpasses at 60-65 mph, enough that my cruise control would drop out. Now, the bus has more unused throttle so the cruise doesn't max out on those overpasses. In fact, it'll cruise way bigger hills now. No change in MPGs IF I GO THE SAME SPEED I USED TO. Please note, I do not recommend injectors that cause black smoke going down the road or climbing hills. The injector chosen should be the one that gives the most max power without black smoke. But the 4104 OEM governor seems to be a different animal since later engines & engines with "truck" governors (Driver has throttle authority) specify smaller injectors. Bus & truck lines used to install smaller injectors because they couldn't control the weight of the driver's foot or whether he would properly downshift when needed. If they used small enough injectors, the driver couldn't hurt the engine & he was forced to shift. My $.02 worth, Jim-Bob | ||
| DrivingMissLazy (66.168.175.51) Rating: N/A |
snip "My cruise used to lose 5-7 mph going over Interstate overpasses at 60-65 mph, enough that my cruise control would drop out". Mine used to do that also. I found that by re-adjusting the cruise linkage so that it came close to but did not go past full throttle, I never had that problem. It only dropped out when speed declined to about 30 mph. Richard | ||
| Jim Shepherd (Rv_Safetyman) (66.82.9.62)
Rating: N/A |
As noted above, a 6V92 with 9G90 injectors and the correct turbo has a DD rating of 350 HP. I have that combination (new injectors and turbo) for sale on the Flea Market (down the list a bit). Jim Shepherd Evergreen, CO ’85 Eagle 10 http://rvsafetysystems.com Bus Project details: http://www.rvsafetysystems.com/busproject.htm (updated 8/7/04) | ||
| Stan (68.150.152.113) Rating: N/A |
Jim-Bob: I think there is something wrong with your injector explanation. If your injectors are pumping 55 cc of fuel per stroke that is over 30 gallons per minute per injector at 2100 RPM. | ||
| John Rigby (24.174.238.253)
Rating: N/A |
Jim-Bob. My 671 was converted over to a truck govenor( one single arm on top ) so I completely control the rpm,s except if I have my foot in it and should not and it lugs. I still dont have one bit of smoke? But The truck gov is probably the reason for ignorance and past problems over the past 18 yeas. With us not having the experince of theses 30/50 year old beuties. I think we are half the challenges they sometimes present. | ||
| Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A |
Stan, you're right. He's off by a factor of 1000. It's 55 cc per 1000 strokes. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher | ||
| Jim-Bob (205.188.116.136) Rating: N/A |
Ah, point well taken. 55 cc per 1000. But don't destroy the relative picture of the engine's performance & the falacy of installing too small injectors for everybody. That's the point I was trying to make. John Rigby: I was just about to install a truck governor when after re reading the description of operation of the FM governor several times I began to see that the governor was not the problem, the injectors were. So I decided to leave it alone & get the rest of the system back where GM had made it. | ||
| FAST FRED (4.245.212.57) Rating: N/A |
The bigest problem with hot rod injectors (besides the added heat & smoke ) can be fuel consumption. Most DD will only operate efficently from 60% full power to 100%. SO if you install such huge injectors that your only cruising on 45% power , your fuel bill will be for 60% power. It is NOT possible to make a DD efficent at every load and speed. Thats why there were 1,2,3,4,6,8,12,16 cylinder versions.... To match the engine to he load. If fuel gets to $4.00 a gallon there will be lots more 55's or 60 injectors sold than 90's. My opinion only, FAST FRED | ||
| John Rigby (24.174.238.253)
Rating: N/A |
Good point Fred. With my N-70 I do cruise at the govenor and only get 6 or 7 mpg. John |