I'm wheeling an '83 bj 42 and in the past year I've overhauled my 3B and I thought that it it would be unjust to refit this bueaty without adding some foced air, but hey I'm no mechanic and I am having some trouble getting the perfomance I'm looking for from my little 3.4L. Some one out there must be able to tell me How much boost is too much. My set up is an AXT and when disconnecting the waste gate I see boost in excess of 20 psi. Is this acceptable or am I living too close to the edge?
how much is too much?
- Thread starter blownbj
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
do you have a pyro? If not get one, and dump fuel into it until she gets some really hot exhaust gas. Someone will tell you the max temp!
How much is too much has been the subject of debate many times...
Some will say keep boosting till something breaks, then you know it was too much.
Some will say 6-7 lbs is enough to keep the speed on hills, cool down EGT's, and still maintain a long lived engine.
Somewhere in between those two is most likely the balance...depending on your needs and setup.
I really have to pick up my knowledge of turbos and diesels. Anyone have any good book titles?
20lbs has to be heating up the air pretty good. Perhaps too much.
There will be a point of dimishing returns with a indirect injected diesel, and pumping losses from the precups. Where that is I have no idea.
I recall some people on this list comlaining of a surging with the AXT above a certian boost. There was a fix posted (It was either here or on the DTLC).
Gauge it with a pyro, if you have not already.
I am sure many more knowledgable then I will post up their thoughts and experiences.
Read post #3 of this thread:https://forum.ih8mud.com/showthread.php?t=56379
hth's
gb
Some will say keep boosting till something breaks, then you know it was too much.
Some will say 6-7 lbs is enough to keep the speed on hills, cool down EGT's, and still maintain a long lived engine.
Somewhere in between those two is most likely the balance...depending on your needs and setup.
I really have to pick up my knowledge of turbos and diesels. Anyone have any good book titles?
20lbs has to be heating up the air pretty good. Perhaps too much.
There will be a point of dimishing returns with a indirect injected diesel, and pumping losses from the precups. Where that is I have no idea.
I recall some people on this list comlaining of a surging with the AXT above a certian boost. There was a fix posted (It was either here or on the DTLC).
Gauge it with a pyro, if you have not already.
I am sure many more knowledgable then I will post up their thoughts and experiences.
Read post #3 of this thread:https://forum.ih8mud.com/showthread.php?t=56379
hth's
gb
- Thread starter
- #4
I do have a pyrometer and since I've disconected the wastegate control I can't seem to get the temps up over 800F but my 3B is equiped with HAC and it's fully adjusted. How can I get more fuel? There is already an intercooler sitting in front of my rad just waiting to get piped in. I'm not scared of power!!
- Thread starter
- #5
I really want to push my 3B to the limit and the north american rep for AXT informed me that number not to exceed is 1150F on the EGT and basically what I'm looking for is a way to get it there even after finish plumbing in the intercooler. More fuel !!
yeah, the max EGT is about right - around 1200F PRE turbo, but it doesn't sound like that seems to be a problem for you - yet. As well, it is usually an excess of fuel that is the biggest culprit with high exhaust temps, not excessive pressure. Although this will contribute somewhat to this.
As far as max boost, I dunno. Indirect injection of the 3B has limitations: pre cups and high compression of about 20 or 21 to 1. Domestic diesel pickups are running mid to high teens, I think, from the factory, but I am not sure of specifics. Hot rodded trucks often see the 40's. Commercial trucks will get into the 30's. But these engines all have some significant differences from a 3B including lower compression ratio, direct injection and intercooling.
This is all probably moot if you can't get any more fuel through the injector pump. Good luck.
-kevin
As far as max boost, I dunno. Indirect injection of the 3B has limitations: pre cups and high compression of about 20 or 21 to 1. Domestic diesel pickups are running mid to high teens, I think, from the factory, but I am not sure of specifics. Hot rodded trucks often see the 40's. Commercial trucks will get into the 30's. But these engines all have some significant differences from a 3B including lower compression ratio, direct injection and intercooling.
This is all probably moot if you can't get any more fuel through the injector pump. Good luck.
-kevin
crushers
post ho
well, this is my findings so far, over fueling didn't cause me any troubles on the LJ71, BJ74 or the HZJ75T. what i have found is lugging the engines seem to cause a severe problem with EGTs. if you rev the engien high enough for a smooth transfer into a higher gear the EGTs come up faster but drop quicker as well. the larger exhaust definately helps in the EGT department...
cheers
cheers
- Thread starter
- #9
I'm running 2.5 inch straight pipe so exhuast restriction is not going to be a problem and my intercooler is nearly ready to go but so far I really have no need to tie it in becuase my EGT just won't come up without more juice. The particular feed pump I have is equiped with a HAC rather than the fuel stop control that GregB had refered to and that's already been exhausted as far as it's adjustment will go. Do any of you guys know about adjusting the injection volume for individual cylinders?
It seems that there are a lot of mis-conceptions about boost, fueling, exhaust gas temperatures, how much an engine can take, and what the maximum of each should be. Let me boil this down for y'all.
--Exhaust Gas Temperature--
- This is the temp of the exhaust leaving the cylendar.
- A "Pyrometer" is used to measure Exhaust Gas Temperature.
- The probe for a pyrometer (called a Thermocouple) can be installed before or after the turbo.
- The melting temp of aluminum is 1190-1215 F. Most pistons are aluminum, so this is the max EGT for uncoated aluminum pistons. This is why 1200F is a max pre-turbo temperature.
- ceramic coated pistons can handle higher EGT's as the ceramic coating insulates the piston head.
- Iron melts at 2781-2799F. It's not the block or head that's a concern, just the aluminum pistons
- EGT's are LOWERED by more boost.
- EGT's are INCREASED with high fuel.
- Lugging or full throttle at low RPM's makes for high EGT's. This is because boost is low at lower RPM, and fuel is maximized with the full throttle.
- If you EGT's are too high, try downshifting! Your RPM's increase, your boost will increase, your your EGT's go down.
- EGT's can get out of control in high mountain areas where atmospheric pressure is lower, making your overall boost lower
- Turning up the boost without turning up the fuel will LOWER your EGT's.
- Turning up the fuel without turning up the boost will INCREASE your EGT's.
- The proper way to get the most out of your engine is to first set the boost to whatever level you want, then adjust the fuel so that the max. EGT's are where you want them.
- What SHOULD your max EGT's be? It depends on how conservative you are. The longer you want your enging to last, the lower the EGT's should be. Anything about 1200F is silly, however.
--Boost Pressure--
- This is the air pressure ABOVE ambient atmospheric (around 14.7psi at sea level) delivered by the turbo.
- The MORE boost you run, the LOWER the exhaust gas temperature if you don't adjust the fuel.
- Without an intercooler, the MORE boost you run, the HIGHER the intake temperature.
- This higher intake temp has an effect on exhaust gas temperature. hotter intake air is less dense, has less mass, and is less able to carry away the heat of combustion at a low temperature.
- anything over about 12 Psi boost will benefit from an intercooler.
- The REASON that an intercooler lowers EGT's is because there is more mass of air in a cool intake charge to carry away the heat of combustion at a lower EGT. The fact that the air is cooler to start with is almost neglidable in the equation... it's all about the mass of air in the intake charge
- this is the same reason that propane and water injection can lower EGT's. It's not because the intake air is colder, it's because cold intake air is more dense, has more mass, and more mass of air take more heat to get to a dangerous EGT.
- How much boost can your engine handle. It depends.
- like EGT's, it depends on how conservative you are. More boost = less engine life. More boost puts extra stress on bearings, rods, wrist pins, head and crank shaft bolts, head gasket, etc...
- Indirect Injected engines can probably handle less boost as a result of the tiny hole in the pre-cup that all that mass of air has to be pumped through. This generates heat, robs the engine of power, and creates stress on the pre-cup, which has been known to crack and drop pieces into the cylendar. However, upwards of 20PSI have been run on Toyota ID engines without repeatable failures. (Don't flame me with anecdotes) I personally don't believe that the upper limit of max boost for a stock 3B/HZ is known!
- Direct injected engines can handle as much boost as the head gasket and head bolts can handle. Boost upwards of 50-60 psi is not uncommon on tweaked out Cummins engines. Some drag diesels run over 150psi. Again, the upper limit of boost after which failure is gauranteed has not been determined for Toyota DI engine. (Again, you can keep your anecdotes to yourself)
--Exhaust Gas Temperature--
- This is the temp of the exhaust leaving the cylendar.
- A "Pyrometer" is used to measure Exhaust Gas Temperature.
- The probe for a pyrometer (called a Thermocouple) can be installed before or after the turbo.
- The melting temp of aluminum is 1190-1215 F. Most pistons are aluminum, so this is the max EGT for uncoated aluminum pistons. This is why 1200F is a max pre-turbo temperature.
- ceramic coated pistons can handle higher EGT's as the ceramic coating insulates the piston head.
- Iron melts at 2781-2799F. It's not the block or head that's a concern, just the aluminum pistons
- EGT's are LOWERED by more boost.
- EGT's are INCREASED with high fuel.
- Lugging or full throttle at low RPM's makes for high EGT's. This is because boost is low at lower RPM, and fuel is maximized with the full throttle.
- If you EGT's are too high, try downshifting! Your RPM's increase, your boost will increase, your your EGT's go down.
- EGT's can get out of control in high mountain areas where atmospheric pressure is lower, making your overall boost lower
- Turning up the boost without turning up the fuel will LOWER your EGT's.
- Turning up the fuel without turning up the boost will INCREASE your EGT's.
- The proper way to get the most out of your engine is to first set the boost to whatever level you want, then adjust the fuel so that the max. EGT's are where you want them.
- What SHOULD your max EGT's be? It depends on how conservative you are. The longer you want your enging to last, the lower the EGT's should be. Anything about 1200F is silly, however.
--Boost Pressure--
- This is the air pressure ABOVE ambient atmospheric (around 14.7psi at sea level) delivered by the turbo.
- The MORE boost you run, the LOWER the exhaust gas temperature if you don't adjust the fuel.
- Without an intercooler, the MORE boost you run, the HIGHER the intake temperature.
- This higher intake temp has an effect on exhaust gas temperature. hotter intake air is less dense, has less mass, and is less able to carry away the heat of combustion at a low temperature.
- anything over about 12 Psi boost will benefit from an intercooler.
- The REASON that an intercooler lowers EGT's is because there is more mass of air in a cool intake charge to carry away the heat of combustion at a lower EGT. The fact that the air is cooler to start with is almost neglidable in the equation... it's all about the mass of air in the intake charge
- this is the same reason that propane and water injection can lower EGT's. It's not because the intake air is colder, it's because cold intake air is more dense, has more mass, and more mass of air take more heat to get to a dangerous EGT.
- How much boost can your engine handle. It depends.
- like EGT's, it depends on how conservative you are. More boost = less engine life. More boost puts extra stress on bearings, rods, wrist pins, head and crank shaft bolts, head gasket, etc...
- Indirect Injected engines can probably handle less boost as a result of the tiny hole in the pre-cup that all that mass of air has to be pumped through. This generates heat, robs the engine of power, and creates stress on the pre-cup, which has been known to crack and drop pieces into the cylendar. However, upwards of 20PSI have been run on Toyota ID engines without repeatable failures. (Don't flame me with anecdotes) I personally don't believe that the upper limit of max boost for a stock 3B/HZ is known!
- Direct injected engines can handle as much boost as the head gasket and head bolts can handle. Boost upwards of 50-60 psi is not uncommon on tweaked out Cummins engines. Some drag diesels run over 150psi. Again, the upper limit of boost after which failure is gauranteed has not been determined for Toyota DI engine. (Again, you can keep your anecdotes to yourself)
denis
(O) toyota nut (O)
Hey Peter I tend to agree with most of your post, but...
I spent some time (and fuel) playing with my friends 24V HDJ80 -intercooled with mostly stockish fuel adjustments- and I found that the max EGTs I could get (~1200F) were acceleration WOT at about 3500 rpm, whereas the mid rpm ranges 2500-3000 were seldom above 900F. The low rpms were low EGT, but that's with the factory very low fuel setting that all 24Vs are well known for. That was racing on flat roads, no big hills for testing slower accelerations. I did not test at very high speeds either. Unfortunately there is no boost pressure on the rig yet.
Behemoth60 said:
I spent some time (and fuel) playing with my friends 24V HDJ80 -intercooled with mostly stockish fuel adjustments- and I found that the max EGTs I could get (~1200F) were acceleration WOT at about 3500 rpm, whereas the mid rpm ranges 2500-3000 were seldom above 900F. The low rpms were low EGT, but that's with the factory very low fuel setting that all 24Vs are well known for. That was racing on flat roads, no big hills for testing slower accelerations. I did not test at very high speeds either. Unfortunately there is no boost pressure on the rig yet.
cruiser_guy
Out of Africa / North Africa
I've got another question for you all. Is it not true that before we turbo'd our 3B engines the exhaust was MUCH hotter than it is now? I KNOW that the one time that my intake popped off the manifold (after the turbo), my EGT's shot up to 1400-1500 instantly (I felt the pop and let off right away but a quick glance at the pyro showed it dropping from far higher than I'd ever seen it before or since. Doesn't this mean that the turbo is actually EASIER on the pistons (lower temps)? Remember the pistons are also oil cooled from below with the piston skirt cooling that the 3B has.
Good post Peter. One of the problems with typed communication is the automatic assumption of knowledge at times with inter-relationship issues such as EGT's and the combined effect of boost and fuel. You post clears that up...
Stone, this is a sticky imo.
gb
Stone, this is a sticky imo.
gb
Tapage
Club 4X4 Panamá
Good Info Behemoth. ! I like this forum, not only one experience or info source .. more experiences with more sourcer are always better.
I need to say, not always the EGT are truth, and let me explain it. If you have 1250 ºF ( max EGT that our Toy engines can handle ) you are noticed about you higher exhaus temp, but if you apply more boost inmediatly you EGT down ..
Easy don't you think, more boost and more diesel .. everithing is fine. But you need to check other iisues, as Behemoth write in IDI engines. 20 PSI are insane in our engines .. if you think in a Porsche engine it was disignet from factory with turbo ( as a hi performance engine ) with 1.2 BAR ( aprox 18 PSI ) with proper pistos and low compresion ..
I mean 20 PSI in a Toy engine with 12:1 compresion its fine, but with more than 18:1 nop ..
I always Thought, if you like the edge and your engine it in good shape 14 PSI.
I need to say, not always the EGT are truth, and let me explain it. If you have 1250 ºF ( max EGT that our Toy engines can handle ) you are noticed about you higher exhaus temp, but if you apply more boost inmediatly you EGT down ..
Easy don't you think, more boost and more diesel .. everithing is fine. But you need to check other iisues, as Behemoth write in IDI engines. 20 PSI are insane in our engines .. if you think in a Porsche engine it was disignet from factory with turbo ( as a hi performance engine ) with 1.2 BAR ( aprox 18 PSI ) with proper pistos and low compresion ..
I mean 20 PSI in a Toy engine with 12:1 compresion its fine, but with more than 18:1 nop ..
I always Thought, if you like the edge and your engine it in good shape 14 PSI.
- Thread starter
- #15
So all that information is going to come in very handy if someone could just give me a little bit of knowledge on how to get more fuel to my engine. I mean even @ 15psi or the very respectable 12psi that I had my waste gate dialed in @ I still won't see 1100 with my air to air installed.
try calling these guys
they offer a fuel enrichment sloenoid thingy
http://www.marks4wd.com/3B-turbo-chargers.htm
also they may be able to offer some imput. other that that, talk to a fuel injection shop, see if you can get larger nozzles for your fuel injectors. that might be the best bet.
they offer a fuel enrichment sloenoid thingy
http://www.marks4wd.com/3B-turbo-chargers.htm
also they may be able to offer some imput. other that that, talk to a fuel injection shop, see if you can get larger nozzles for your fuel injectors. that might be the best bet.
Tapage
Club 4X4 Panamá
wouu a lots of money for my little wallett .. 
- Thread starter
- #18
Ya! That's a little rich just to make my cruiser run rich. Has anyone ever rebuilt there own injection pump before? I was thumbing through my engine manual and theres a section in there about adjusting the fuel delivery volume for each cylinder. How hard is that to do?
Tapage
Club 4X4 Panamá
In my concept, diesel pump rebuild is a Diesel Lab job .. here are not cheap, but I pay for ti .. is not easy work to do ( in my concept ).
cruiser_guy
Out of Africa / North Africa
Tapage said:
David, I'm with you. I wouldn't touch the diesel injection pump either. That's what all those neat machines in the injection shop are for.
