4.8 Exhaust Manifold

[J@coBez]

My 2003 4.8 met 175 000 km op, se exhaust manifold is vol krake. Die voorste manifold is amper heeltemal af tussen nr.2 en 3 en die agterste manifold het op nr.5 poort n lang kraak, dis aan die Engen se kant. Aan die buite kant is daar +/- vyf lang haarlyn krake wat minimaal deur blaas.
Kan iemand my dalk raad gee oor hoekom die manifold so gekraak het?
Het iemand dalk n manifold waarvan hy will ontslae raak?

[jeanne.volschenk]

Jis,

Ek kan jou nie se wat jou probleem is nie maar ek het 'n 4,5 Std manifold en ook 'n branch. Of hulle pas is 'n ander vraag ?

Cheers

JV

[Peter Connan]

Jaco, did you perhaps do any deep water crossings with a hot engine?

[J@coBez]

Nie wat ek van bewus is nie ek het die Patrol nou eers ses maande. Ek en n friend reken die uitlaat lug spoed is te vinnig a.g.v die free flow exhaust wat op die patrol is. Ons kan verkeerd wees maar die manifold lyk of hy baie warm word.

Jeanne, dankie ek sal jou in gedagte hou maar volgens wat ek in die manual sien is die 4.5 n eenstuk manifold met een exhaust sensor waar by die 4.8 n split manifold is met twee exhaust sensors is.

[tour de frans]

Goeie Dag
Ek weet nie waa jy n manifold kan kry, behalwe agente nie. Maar ek het n vraag wat jy kan nagaan oor hoekom die manifold dalk kon kraak.
Het jou kar n chip in? Unichip? Wanneer n chip gefit word word die tyd voor op die engine na maximum gedraai om n wyer skaal te kry vir verstelling. Het iemand nie dalk die tyd terug gedraai nie? Of al het die kar nie n chip in nie, is die tyd reeling nie te stadig nie?
Te stadige tydreeling (timeing) raak die exhaust temprature hoer as normaal en kan die exhaust kraak. MAW as die tyd te stadig is gaan die ontbranding uit sie silynder in die uitlaat in. Dit veroorsaak die exhaust om warmer te raak as normaal.
Maar jou verbruik sal ook nie te goed wees nie. Net n gedagte.
Groete
Frans

[beast]

My 4.8 has also had two cracks on the manifold. I had them welded. The exhaust place said to me that his view was that the engine runs too hot, which I agreed with. This guy said that there was people in the Eastrand that built new manifolds.I have just returned from Sordwana and now my gaskit on the exhaust has also blowen. I have taken the aircleaner of and changed it with an open airfilter. I have also but a freeflow on the exhaust, which I must say changes the vehicle. I have more power and fuel economy seems much better. The engine breaths better. Will keep you updated as I am working on getting more power with reduced consumption. Nico

[J@coBez]

Nico,

I looked at a few options:
One would be to weld the existing manifold and keep the free-flow that is currently on but because of the amounts of cracks I feel that the manifold will not be 100% and I still feel that it can be the exhaust creating problems.
Two would be to buy a new manifold not a real option as the set is R9500 at Nissan and R6500 at a Nissan part supplier in Cape Town, then the gasket is another R1250/set.
Option three would be to do a stage one conversion that I feel the most comfortable with due to the fact that every thing match and this will put my mind at ease that every aspect is looked at. I spoke to Maus conversions and they recommended a stage 1 conv. @ R9500 excluding a Branch @ R4500. Rob Green also recommended that stage 1 would be the best @ R13600 excluding a branch that would be in the region of R8000 extra due to ceramic coating for under bonnet heat. Then SAC also came withe a stage 1 conversion @ R10500 all include. All stage 1 conversions are basically the same, includes Chip, 63mm SS exhaust and a air cleaner with the exception of SAC that includes a Wild Cat Branch.

For now I will go with SAC for now as they are the most affordable option at this stage. By doing this conversion I also hope to improve my fuel consumption as I am on 3.5 kilometers per liter. Will have the conversion done in the next two weeks depending on my work will post the results of dino.

Thanks Jaco

[Peter Connan]

Jaco, my only comments are as follows:

Firstly, at 3.5km/l there is obviously something wrong. I now firmly beleive that if there is something wrong with a system, that problem should be found and repaired, rather than trying to "modify it away", as the modifications might not address the root cause of the problem. In this case, it is very likely that it would, but there aren't any guarantees.

Rather start by getting it on a dyno and a four-gas analiser, and try and ID the actual problem.

Secondly, depending on the use your Patrol sees, I would think carefully about the free-flow air filters that come with most of these stage 1 conversions. If your car is used on the road and perhaps sometimes on the beach, such as for towing and launching a boat, fine and well, but if you drive dusty roads, I would stay with the standard filter. The free-flow units are not nearly as effecient, and the life of your engine will be impacted. Furthermore, because their surface area is generally smaller, they block up more quickly and need to be replaced more often, and they are considerably more expensive than the standard filter. Ask Tinus Lotz who has been through this exercise with a 4.8.

Lastly, with a stage 1 conversion, all the elements are not matched. The most important matching operation, that of the manifold to the head, is only done on a stage 2 conversion, but probably not worth the extra expense.

[AndriesS]

I'll have to agree with PC on the air filter. I'm also very weary of branches on a 4x4. they tend to generate more engine bay temps , I guess a ceramic coating will help. Also a number of branches I've seen is really just a pipes welded together without much design , this is more so on nearly once-off where there market is small and the effort for the design vs value from the fabricator is just not worth it.


I would like to get feedback on decent freeflow's made here in PTA/Centurion. I would like to change it but don't want this booming in the rear you find with some systems. Also don't want the coke can on throttle off sound.

[Tinus lotz]

i spent a bit of time on this topic and after speaking to the guys other than the ones that sells the stuff the 4.8 manifold is as good as branch no one got more hp , if your manifold is broken and a branch is cheaper go for it . 3.5 is wrong big time i only get that when driving deep sand and very slow ......
in town between 4.8 and 5km/l on the highway at 120 5.5 to 6 easy
leave the k&n filter for the race cars i did it and took it off very soon !!!
the japs spend years developing a system that works all round i had to clean mine about every tank !!!
something that does work is a snorkel it puts cooler air in the engine when driving slowly
it made a diff not massive but it helps
has your trol got a cat inline ????