Jump to content
SAU Community

Recommended Posts

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..... :D

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:

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.

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..

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.

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..

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.

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

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.

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.

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!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Doing a refresh of my 33 and can see a few websites stating they sell the entire main carpet for our cars, but they all have generic photos which is fine, i understand they are custom made to order.  Just seeing if anyone has got it done or had any experience with this, as i would only want to do it if the fit and finish was as good as oem https://carmatsdirect.com.au/products/moulded-carpet-or-vinyl-for-nissan-skyline-r33-1993-1998-coupe https://knoxautocarpets.com.au/moulded-carpets/nissan/skyline/skyline-r-33-1993-1998/
    • Any plans for E85? If so, add flex fuel sensor.   I'd probably add in the sensors I mentioned above if the Link will support using them for engine protection. With water pressure, you need to be able to effectively set it that "If temp > X, and pressure = atmospheric, shutdown" as at running temp, you should be able to read pressure in the cooling system. If pressure suddenly disappears, it means the water went some where, and this is a quicker reaction than waiting on water temp to go up (Which, can take a little longer than you'd like, considering it now has to wait for hot air to heat it up) Oil pressure, Oil temp, both would be on my list too if you're looking to add sensors. Wideband O2. And at least one EGT sensor. If you're feeling deluxe, put in individual runner EGTs. Single EGT sensor is more so forget about a specific number, get used to "What is normal EGTs", and then keep an eye on it, if it starts going away from "normal" it's a sign something is wrong (Also, things like the tune can still start going out of spec, but EGTs may not show it, for example one injector starts running leaning, so ECU richens everything up, now 5 out of 6 cylinders are rich, and running cool, with one cylinder lean and running hotter, so it's not perfect) Then there is your other things to look at non sensor related, but you may have already done, or have underway, and that would be things like building a sump for more oil, and better oil control under high G-Forces (Cornering, brakes, acceleration). Basically, the above is worth looking/thinking about, if the ECU can do protective stuff with it, and you continue to use it how you are (Drive it to the track, thrash it, drive home, repeat once every 3 to 4 months)
    • Can also confirm these work a treat for most balljoints and bushes. If you have access to a big rattle gun, they make the job so much easier and quicker, compared to using a socket wrench or shifter on the c-clamp 👍
    • Its sort of street but got used for circuit sprints on account of I never drive it on the road because I dont have the time to spare. So it usage was sits around for months at a time then gets driven either 50 or 250 kms to the track followed by 20 laps followed by 50 or 250kms home followed by stuck in the shed until next time. So yeah neither fish nor fowl. Just dont want to break it on the track as a preference. Hence the fairly short sensor/mod list. Probably more worried about it pinging itself to destruction more so than anything oil related.
    • My thing I'd be doing, is pulling it out, and just getting the tune cleaned up for now. Before that even happens, checking over everything, like vac hoses, fuel hoses, etc. No point dropping thousands on sensors if the moment you start it back up all the oil leaks out, or it has massive vacuum leaks etc.   But really, to know what to do, depends on what your use case is. Hard core track car? Throw most sensors available at it. Street car, I'd probably just run oil pressure, oil temps, water pressure, water temp, probably fuel pressure too. I don't know exactly what the Link can handle and do with those though. And if it's mainly just to cruise the streets, rather than mountain runs, you can probably skip most of the above if you've already got them in as gauges and warning lights.   PS, inb4 "sell it and buy a modern sportscar"
×
×
  • Create New...