Hi,

I am building my 350Z with Vortech V3 and custom piping. Last weeks me and my brother had a lot of conversations about topic draw through and blow through MAF setup. He basically say that draw through is only one option to go, but I disagree and I do not like the negatives comes from draw-through setup - like need to recirculate air shortly before SC and in the same time having MAF mount as far as possible from BOV recirculation because of turbulences, potencial lag, leak problems and so on... I think we do not need to have a conversation on this topic.

However, I would like to ask you guys, how did you achieve the tuning of blow-through mounted MAF setups? I mean, I do have Osiris Tuner, I already tuned the NA car myself and got to 290whp, but I guess it is going to be much more difficult to tune blow-through setup, right? For NA, I just played around with fuel and ignition timing, A/F ratio setup while carefully watching knock sensor, response... and that was it. But now, I guess it is going to be much harder with blow-through, any advice appreciated and yes I have used a search function before asking this help ...

Please any remarks, what to do, how to approach with the tune, what was your biggest problems, do you have some baseline map or anything useful? I guess I put the ignition timing down for the start...

Thanks a lot!

 

I am not a huge supercharger guy so I will yield to the ones that are...and there are some smart ones here...

my immediate question would be - do you have to recirculate? can you dump to atmosphere?

 

Hi,
thanks for your question, that is one of my reasons to go with blow through setup, this way I can dump to the atmosphere - as I have stated in my post. With draw through setup you can't do that, because the air has been already metered and the MAF has to be before the BOV.
I would like to stick with the topic about the tuning part, the topic 'blow through vs draw through' is so complex that 50% of people wants this or the other... If doing right, I believe that both approaches can work well. However, I would like to prefer blow through setup even despite the fact that the car has just a 'simple' MAF that is not suited for metering pressurized air and not only becauseoof that it is going to be a nightmare to tune.

 

That is a common misunderstanding of modern MAF sensors. Modern MAF sensors are MASS airflow sensors rather than the often incorrect thinking of them as volume flow sensors. A MAF will pick up blow through just fine and will account for the change in density due to boost.

Blow through right before the plenum and have your blow off valve before the MAF and you will be fine.

If you did not change your intake piping diameter or injectors, tuning should be pretty straight forward especially with low boost levels. If you run out of MAF scaling, adjust your K multiplier up and multiply the inverse by the maf tables to extend them.

You can pull 1.25 degrees per psi of boost as a conservative start point, but timing should be done on a dyno.

 

I don't understand how you'd recirculate air once it has past the MAF but before the TB? But plenty of examples of this on many vehicles. I wouldn't reinvent any wheels and keep it simple.

 

Thanks, yes that was my thinking too that it shall not be such a problem to tune it as there are plenty of cars out there and everyone was telling me how it is impossible to tune the blow through system, I was just fed up with those conversations between blow through and draw through... It is hard to cope with all those 'engine experts' telling that draw through is only the right way to do it... Most of the kits come with blow through setups so it has to be a reason for it that you have just mentioned. On the other hand, why some kits are designed to be draw through (Stillen SC kit or JWT turbo kit for example) when this has so much negative aspects, there still has to be some opinion why to do it this way, right?

But for me the biggest reason was to simplify my blow-off setup and the smoother drive ability as it is going to be closer to the plenum, plus I can keep most parts stock, the MAF where it is, no wire extensions and stuff like that...

 

I am sorry but you probably do not understand the difference between blow through and draw through setup. With draw through you have your MAF before the SC, so you have to recirculate the air back to the system, but you cant do that before the MAF, because you have already metered the air > you have to recirculate behind the MAF and be careful not to cause turbulences inside piping close to the MAF as it would spoil the values that the MAF meters
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I don't have experience with the VQ, but I personally tuned my turbo 240sx and converted it from draw through to blow through. I assume the principal is the same. Basically it ran slightly leaner when converted. I also exploded the maf but that was a different issue.

 

Back to the tuning part, so the approach is going to be as follows :

1) I will put down ignition values to be safe there
2) setup my AFR targets
3) set the fuel compensation table to 100%
4) log and watch real AFR vs targets - play around with MAF constants to get closer to target AFR and use compensation fuel table only for fine tuning

Am I right? Somebody is saying that I shall tune using K mupltiplier, but I believe I do not need to touch it when the MAF and the injectors are stock, right?

 

nah...I dont you're right - I appreciate the opportunity to learn something!

I gotcha ... Im most familiar with the ATI Procharger and Vortech, where the MAF is after the blower, the recirc valve is before the MAF

but I'd imagine a roots blower, the MAF is before the blower ... how does the gen 1 stillen roots blower handle this?