Fitted my own modified inlet manifold ......

[Sil8ty]

Just lettin you all know i fitted my own "Sil8ty" modified inlet manifold (with T/Body at front) on the weekend with fmic.. And it works a treat.. Had been told by a lot of people that it wouldn't work.. But i actually fitted bungs in all inlet runners to measure boost difference from front to back, finding very little difference from front to back.....

I aint to engineer, but i thought that i would share it all with you..

Will hopefully have some pics for you guys that want to have a look... :uh-huh:

[sn00p]

yep pics would be easier to understand

[Sydneykid]

Hi Sil8ty, "Very little difference" might = too lean in #6 and bang. Boost does not equal flow, so be very carefull, I have tested a lot of "throttle to the front" moves. ALL of them lean out #6 and to a lesser extent #5. Put the highest flowing injector in #6 and the next in #5, that will help.

[Sil8ty]

But wouldn't you say less pressure in back cylinder may represent less air flow?? Do ya think Sydneykid getting it on a dyno and do individual cylinder temp tests this should give an indication (MAYBE) on cylinders suffereing in higher exhaust temps???

Will take note of it.. If any thing i may have thought the #1 cylinder may not get much air as it needs to do a 90+ degree turn to get to it... So far so good......

This is all a touch subject.. I have seen many posts on this subject..

[Clint32]

Yes first cylinder will get less air with the same fuel, so it will be rich, the last ones will have more air and not enough fuel so lean. If the cars running rich it would probably not be a problem, but it ifs tuned on the limit it may pose a problem, just be carefull.

[Sil8ty]

Yeah i get ya.. Car is no extreme machine, only FMIC, Turboback exhaust, filter, Bit of extra boost, Cold Air Partion, Timing adv.. Should still be okay.. Was really rich before fitting the cooler....

Thanks every one for feed back, will hopefully have pix of it tomorrow..

[JimX]

Can cylinders running too lean be detected by spark plug colour? I have a front-facing plenum and I've no doubt that cylinder 6 runs leaner than cylinder 1, but I pulled all the plugs out and checked after around 5000km and number 6 was a healthy light brown colour, and number 1 was a little darker and everything else something in between.

So I don't think I'm running too lean overall, just that the rear cylinders are running correctly and the front ones a little too rich. But there is very little difference in the plug colours, so it's not like number 1 is fouling or anything.

[walkoau]

please post pics.

[Sil8ty]

Damn digital cameras.. Will have them tomorrow now..

[Sydneykid]

Hi JimX you can sure tell by the spark plug colour and what yoiu are describing is most certainly lean to rich rear to front. Primary exhaust manifold temperature is also another, as is indivual cylinder air fuel ratios.

I have posted this a lot, this is what we do to help prevent detonation in #6 and #5, it does work, it increases horsepower as well. Have your injectors flow tested and put the highest flowing one in #6 and the next highest in #5 etc.

It is not unusual to find 1 or 2 injectors out of the 6 that flow 3 to 4% higher than the average. This is more than enough to make a difference and for less than $100 it's easily worth it.

Hope that contributes to the knowledge base

[Jigga]

this is y you don't trust home made engineering, heard of this problem many a time the standard plenum is designed for most efficient flow to each cylinder evenly when you totally fu** up the flow characterists of the plenum by moving the inlet what do you expect ur better of gettin some thing thats designed and engineered to do the job properly like a greddy inlet manifold and you shouldn't have the same problems.

[Warpspeed]

A very great deal depends on the rate of airflow through the plenum.

If you think about it, airflow at idle is going to be pretty even with any type of plenum. It is only when air velocity starts to rise to high figures that the air distribution begins to become more uneven.

I have heard so many times about this terrible air distribution problem with the stock GTR inlet plenum. I would like to bet that a stock RB26DETT running stock boost and power levels, has a pretty good internal air distribution. If you look inside the plenum there are steps, ribs, and all sorts of strange internal features to break up the airflow to give more even distribution.

I bet the Nissan engineers spent quite a bit of time getting this feature exactly right.

Now, some guy builds up a 950 horsepower GTR engine, and suddenly the air distribution in the stock plenum is crap. The air velocity is probably something like three times as high as stock, and it just piles up at the back, and sucks all the flow out of the front runners.

So he replaces the stock plenum with a Trust super plenum or something similar, and the problem goes away. Some guy with a stock GTR engine pays big dollars for that same plenum, because "it must make big power". It would be a complete waste of money on a stock engine, and make no measurable extra power.

The thing to realize is that at near stock power levels you can move the throttle body to the front without any very serious problems arising. But if very high power levels are anticipated, cylinder to cylinder air distribution needs to be taken a bit more seriously.

Maybe your engine needs a big dollar plenum, and maybe it does not. But do not expect massive power gains from one on a mild engine.

[JimX]

Originally posted by Sydneykid

I have posted  this a lot, this is what we do to help prevent detonation in #6 and #5, it does work, it increases horsepower as well.   Have your injectors flow tested and put the highest flowing one in #6 and the next highest in #5 etc.

Where could I get that done? Can I wait while they do it? Thanks for all your helpful advice!

[T0nyGTSt]

Midas can do flow testing for cheap.

The Bankstown one is good as the owner has a 390rwkW GTSt...

I guess he knows something about them

T.

[JimX]

Would flow testing be part of an ultrasonic cleaning process? May as well get both done at the same time.