Q45 TURBO PROJECT

[qsiguy]

you'll run out of fuel and maf before you run out of block strength.

I agree. From my experience/data logging, I was pretty much maxing my MAF and stock injectors at 8-9 PSI of boost. I could increase fuel pressure a little and squeeze more from the injectors but the MAF needs to be addressed. Maybe a simple offset of the output voltage would do the trick. Still, without upgrading both components you will be pushing it to break maybe 10 psi.

On one run at 8 psi of boost...6725RPM (2nd gear) / MAF= 4.94volts / LH & RH injectors at 92% duty cycle @ 97 mph, wide open throttle

Not much more to extract from these stock parts.


Modified by qsiguy at 12:41 AM 3/5/2009

[elwesso]

why not just increase the cross sectional area the MAF element sees and offset the voltage accordingly...

[Carl H]

the nissan maf system can read up to 5.15v before it is completely railed...altho going to a z32 maf will allow for i'd say around another .5v of metering capacity or close to 5-6psi more boost.

[PanzerAce]

and i also agree with the detonation resistance. really, thats the main goal with any design, and making something stronger, but more prone to detonation is just walking backwards.

i am interested on how much a factory vh can take and for how long. id be a very happy person if we can make them live around 450-500 with proper tuning for any decent amount of time.

time will tell, time will tell.

I don't see any reason you guys couldn't hit that on a stock block. I think the biggest issue people using stock engines are going to face is just getting the manifolds to flow enough air. Sure, the stock design isn't terrible, but it isn't the greatest either.

I'm actually kind of suprised that nobody seems to be going for centrifugal SCs yet, since that's probably going to end up being the best method, especially since we aren't talking earth shattering amounts of boost.

[qsiguy]

I've seen a few people install the element in a larger tube. End result will be the same. For me, offsetting the voltage electronically would probably be the simplest. The ECU tuning adjustments are easy once you check map trace with the offset active.

[LEMHEAD16]

QSIguy

How much HP/TQ are you making at that load?

[qsiguy]

Sorry I don't know the hp/tq. Never made it to the dyno post turbo and at the moment it's down to replace the radiator and install a transmission cooler and a few misc. repairs/upgrades. Not sure when I'll make it to the dyno.

[elwesso]

Shane how hard do you think it would be to add 555cc injectors and reprogram?

[Carl H]

just installing and retuning the ecu for injectors is easy as...again its tuning the ecu which is the trick.

[John Dixon]

If you've got room you could just put a 'Y' on the intake then put the MAF on one side and double the k value in the map. Works on Z32 well.Fitting a Z32 AFM will NOT give you more scope, its max voltage corresponds to a lower air flow than the Q45 one. the Q45 maf is used as an upgrade on Z32.Don't really understand the idea behind offsetting the voltage, the meter will still max out and stop reading at X amount of air flow - the actual indicated voltage at that point is immeterial. I should imagine the ECU input A/D will only read just over 5v anyway.

[qsiguy]

Shane how hard do you think it would be to add 555cc injectors and reprogram?

Some of these other guys would know more than I on the injectors since I have never done the job but I have been under the plenum. It didn't look like it would be too difficult. I looked into it but bagged it for budget reasons. The tuning would take some time but wouldn't be hard.

I've played with some offset circuits in the past. I would have to put the MAF on the bench and run some simulations to figure out for sure if it would work. You can offset the Vref or the Vout. If I offset the Vout you may be right that it would still max out at the same airflow. If I offset the Vref I may have more control over the output. I have not messed with it yet so this is just theory at this point. A proportionally larger tube may be easier.

[Stinky]

its max voltage corresponds to a lower air flow than the Q45 one

Actually, I don't believe that's incorrect. While the Q45 afm is physically larger it reaches the max usable voltage (5.12v I believe) at a lower air flow making it good for less power. I can't say I've ever heard of anyone going from a z32 to a q45 afm.

The reason for a voltage offset is because the "max out" is actually due to the afm outputting a higher voltage than the ecu can read (5.12v). If you offset the afm output voltage the afm will read more air before the ecu actually sees the 5.12v.

[qsiguy]

The question is will the MAF output higher than 5.12 v. I've yet to test it so when I get around to it I'll post it. I have a spare MAF so maybe I'll wire it up and fire up the leave blower and see how high it will go!

[Carl H]

the maf might be able to generate higher voltage but the a/d converter in the ecu rails out around 5.12v.

[qsiguy]

I realize that, that's why I would like to just offset the output to drop it .5-.8 volts and retune the ECU. This would let me up the boost a bit more. I just need to make sure the MAF will keep reading/increasing over xx amount of airflow.

[Carl H]

i think going z32 maf is proly a better way to do that then to try and fool the ecu...rescaling maf maps can get tricky...its possible but tricky to do right.