Jump to content
SAU Community

Recommended Posts

  • Replies 141
  • Created
  • Last Reply

Top Posters In This Topic

if map sensors were so bad then all aftermarket ecu's wouldnt come with map sensors in the first place.. you only UPGRADE to aftermarket ecu's not down grade.. at a given power stage a afm will become a restriction weather it be 600rwkw or not, at some point it will end up restricting power or the abilitly to tune.

Ho rbs13, you posted "if map sensors were so bad then all aftermarket ecu's wouldnt come with map sensors in the first place"

Nobody said MAPs are bad, just that AFM's are more accurate. The reason why some (not all) aftermarket ECU's use map sensors is because they are cheaper and can be integrated into the ECU itself (ie; small in size). Plus setting up an AFM on a car that does not have one can be tricky, no such trouble with Skylines that already have AFM's.

"you only UPGRADE to aftermarket ecu's not down grade"

The are plenty of OE ECU's that prove that wrong. They are way smarter and faster than most aftermarket ECU's. I would argue that the standard R32 GTST ECU (and it's 15 years old remember) is "smarter" than a lot of current aftermarket ECU's.

"at a given power stage a afm will become a restriction weather it be 600rwkw or not, at some point it will end up restricting power or the abilitly to tune"

True, but if that level is higher than your target power, why worry about it? Enjoy the smoother running and better fuel economy of an AFM equiped car. Two Q45 AFM's will handle 850 bhp, so there is plenty of room to move up.

There is a place for both MAP's and AFM's, but on road only and road/track Skylines, the AFM sensored ECU is still very hard to beat.

Hope that clarifies

Originally posted by rbs13

if map sensors were so bad then all aftermarket ecu's wouldnt come with map sensors in the first place.. you only UPGRADE to aftermarket ecu's not down grade.. at a given power stage a afm will become a restriction weather it be 600rwkw or not, at some point it will end up restricting power or the abilitly to tune.

hrmmm .....

Who said map sensors where that bad?

Generally the main reason why people lean away from AFM's is because the power level they are after.

If they were building the car to be better on petrol (not likely) they would not ditch the AFM for the Map sensor.

600rwkw you wouldn't bother with AFM's unless you were going to run 2 Nissan Q45 AFM's.

What I like about AFMs is that they are far more tolerant to slight changes in engine tune. They actually measure airflow directly, and that is a very important advantage in my opinion.

A MAP sensor cannot do this. A map sensor assumes that at a certain given manifold pressure, flow through the engine will be xxx CFM of air. But what if you move the valve timing slightly, or fit a different exhaust turbine housing ? You get to completely remap the engine because the breathing characteristics have now significantly changed.

This is fine for a competition car that spends more time on the dyno than on the track. But what if you are just an average joe with a car port at home, and you want to try a different exhaust muffler ? The change in exhaust back pressure might really screw up your mixtures, probably not by much but it will have some effect.

With an AFM, your new beaut muffler might change airflow, and the AFM just alters the fuel to suit the measured increase or decrease.

So, apart from all the theory, there are also practical considerations as well.

As far as restricting power, well, atmospheric pressure is around 410 inches of water, so if your airflow meter has a four inch water pressure drop, you are still getting 99% of atmospheric pressure and density. Not enough to really worry about I think.

The induction temperature at your cold air pickup point might be 300 degrees Kelvin (at 27C ambient), if you can lower this by 3C you will pick up 1% in air density which will easily compensate for the drop across your AFM.

So some guy fit two huge Q45 AFMs to reduce the imaginary horrible power loss, and then fits a couple of crappy pod filters right behind the radiator. I cannot understand the logic behind any of that.

the reason im putting RB20 turbos on is that i already had one, and they are cheap, when it is all up and running and if its really laggy, ill might have to consider a RB30 bottom end. But anit these alot weaker than my bottom end. What type of internals would i have to put in, like pistons? chankshaft? gearbox??

R32 GTSTT, please do a search to answer the rest of your questions. Pistons, crankshaft and gearbox for a RB30 have been discussed a million times already.

You still haven't told us how much power you're looking for. Do you expect to drive this car on the street?

well i wasn't to concerned about the power it wil make. I have a open mind about it, i just want to make the most power out of these 2 turbos at the moment. I do plan to drive it on the street, and drags aswell. If it is extremely laggy then i will consider smaller turbos, or doing a RB30 conversion. The main concerns i have at the moment are if my fuel pump, injectors, and afm, and ecu. Just wondering if u guys think if any of these things will be holding back my power?? Cheers

yer cheers, i think i will, just have to find the right place to go in perth. Say the stock turbos come on boost at 2800, ppl r saying two wont spool up until twice that say 5500rpm. But doesn;t the car produce more exhaust gas between 2800-5500 than it does from 0-2800. So wouldn't it take much less than twice the rpm??

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



  • Latest Posts

    • Nah, they'll do it without a receipt, tell em roughly when it was, that it was cash, youll likely only get store credit, but that gets you some dollars towards the newer better shovel, or other item you need/want later.   Still take it back and have a crack at returning it.
    • Nah. Was just wondering if you were having a small stroke or if there was some slur/gaf/inside joke that I wasn't aware of.
    • That was a fark up, it's Salamanca Place I was thinking of. And now I'm curious as to what potential slur/gaf I have caused with Salamander Road, ha ha!
    • Actually everyone on the roads was really well behaved. The only person that did any minor tailgating was a local hoon in a Turbo Focus. Unfortunately we weren't going the same way so there was no grand initial D touge battle. Lots of people pulled over and let me through. The amount of "Hey man nice car, omg skyline, nice 34 man woo" was suprising. Like really suprising. Like almost annoying. My partner was obviously surprised, she'd never seen anyone in the real world point out the car/like the car/want to chat about the car before, so to have like 3 people per day mention it was notable, I could finally say SEE? SOMEONE THINKS THEY'RE COOL. Everyone was also pretty suprised about the weather. Every day was dry and about ~13-14C. Mount Wellington had a sign that said they close the gates at 9pm and I was heading up there at about ~7:30. It was VERY apparent that conditions were getting significantly worse by the minute on the way up and down. The road on the mountain was terrible though, it's no driving road. I have various suspension related questions now. Luckily it was only about 20 minutes from where we were staying to the top of the mountain as said Google maps. We only had the 2 nights in Hobart. We went to the Farm Gate Market though which was really good - And went down to the Hastings Thermal springs/caves down there during the day. I'd definitely be up for going back again, so luckily there's a few more sights yet to see. Didn't get to do the west coast/queenstown/cradle mountain so this was supposed to be a 'scouting' trip anyway of sorts if I were to one day do/take part in/organize a more car-focused trip. As for the boat, it wasn't bad. Well it was bad, but not in the way you're thinking. We did the night trip which leaves at 6:45 (though you have to be there ~2 hours earlier) and arrives the next morning at about 6am. There is nothing to do on the ship. If you plan accordingly and bring a book/tablet/show to watch/charger you can just chill out, take some Travacalm and just sleep through it. The food there is an extremely basic buffet that costs $32 a plate, or $14 for a $3 pizza. The way back we had a travel kettle and a few different types of cup noodles and made our own tea/coffee in the room. This was a far superior way to do it. At the very least book one of the rooms with beds. I guess as we were in the off season we didn't have room mates. You get an option for rooms with 4 beds (2x bunks) or a room with just the two bottom beds. There's also some option for a deluxe queen bed but it's much pricer. We've been on sleeper trains in Asia before so we figured this is similar (and it was)
×
×
  • Create New...