Blow thru conversion done! Question...

[97stanger]

Just finished with my dad finishing up my blow thru conversion. Before this I had a SCT BA3000, vortech mini racebypass valve setup as draw thru. I changed over to a Vortech mondo valve, and a VMP 3" housing, HPX slot style maf now. Heres how it looks:

The car fires right up, absolutely no problems. The only problem is it wont hold an idle, just dies. When I give it gas trying to hold the idle my a/f goes from 14.7 to all wacky, so we cut it off. Should this be normal? I can imagine the car needs a tune...just wanted to make sure this should be normal.

 

[forcefedhatch]

Yeah it's normal the maf voltage signals are wacky after the initial start because your old tune is running off of the scaled table till the wideband heats up then it runs loop from that to adjust the tables, then the maf voltage is throwing things off, it's trying to correct itself, but it can't cause the actual signal is different in reading because the maf scales are now different with newer slot samples of air it may be reading more accurately and now the ecu has to be tuned for the indifference of less or more voltage/reading.. Basically until the wideband sensor heats up it runs on just the preset table, then once warmed up the two signals are not in complete sync as they once were with the older design.. It is now more efficient and needs to be calibrated for that..


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[97stanger]

thats what I figured, thanks a lot for the info forcefedhatch. Good stuff

 

[forcefedhatch]

No prob bro.. Been there a few times lol..


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[shiftmx55]

Set up looks awesome!

 

[97stanger]

Thanks a lot man! Just getting anxious to get this car tuned and to see how it responds to the meth setup

 

[Ferocious]

That looks MUCH better than before. Nice job Mike.

 

[stprorolla49]

Nice work Mike, can't wait to see the numbers!

 

[97stanger]

Appreciate it fellas, I'll be sure to provide updates

 

[robb15033]

That's one of the most beautiful things you can ever see.

 

[97stanger]

That's one of the most beautiful things you can ever see.

Haha thanks a lot for the nice words, lots of time and money under that hood

 

[Dalamar]

Looks great man.


I'm curious, what are the pros/cons of draw through vs blow through? why did you swap?

 

[forcefedhatch]

Blow thru is more accurate because it can only meter what's being introduced to the engine, draw thru can sometimes even pick up stiff crosswinds and mistake them for metered input, rare but is an actuality, plus the main benefit is atmospheric release of pressure in the system, in draw thru it has to have any pressure release( bov, diverter valve, etc.) reintroduce the air( recirculated bov) to be metered to prevent a rich or lean mixture of fuel because of the unread air. Blowthru can released atmospherically as long as the bov/diverter valve is before the maf so it can read the lack of air before its introduced to the engine chargepiping.. Draw thru before power adder, blow thru in the charge piping after the power adder..


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[Dalamar]

Thanks for the explanation.

I've wondered if that would be beneficial for my combo, but didn't know much about it.
Always wondered if when I let off the throttle, and the compressed spiking back through the line messes with the MAF.?

 

[forcefedhatch]

No it wouldn't hurt the maf unless there is a boost/charge leak at the maf, then it would mess with the overall performance in a blow thru system, in a draw thru system it could because if that already metered air isn't re introduced to the maf it will throw off the readings.. The reason is, that air has already been accounted for and the fuel trim has been determined, but if that air is released and not immediately reintroduced to be read, you have a dead spot in the fuel trim and nowhere for that fuel to go but to either run you rich, or puddle up in the intake and cause predetonation off of compression stroke, and backfire then in turn burn the next strokes fuel during the back fire, and then in turn again leaving you in a now lean condition.. Boom knock goes up, intake temps rise, not enough fuel to compensate and then burnt up pistons/ring lands..or even worse cracking a piston due to extreme heating then cooling( 1300+*F down to 500+\-*f )in the matter of fractions of a second expanding and contracting the metal to fast to be able to rebound and thus weakening and cracking or shattering them..



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[forcefedhatch]

Ok I really think I could have overdone that one lol.. Either way I'm just a dumb redneck who played in EFI 101 too much lol..


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[97stanger]

hahaha good stuff. Dal, the reason I switched is because I had all intentions of just swapping my draw thru mini race setup to a draw thru Vortech mondo setup. WRONG MOVE. I swapped valves and the car would just surge like crazy. It is too big of a valve and basically just dumps tons of air right before the maf, causing my surging. So thats what caused the swap. After doing tons of research it seems like there is tons of benefits to going blow thru, as forcefed basically named them all.

New tune/meth tune setup for Friday 4/20

 

[Dalamar]

Sweet man, sounds like you're doing it right!

 

[97stanger]

I'm actually surprised you are running draw thru on your turbo setup. Hows drivability? How much psi are you pushing and what bypass valve are you running?

 

[mikey94gt]

I wanna see what you make. I love my car with the blow thru, did you notice the car was way easier to drive after the conversion? Throttle response was much better?