I recenctly drop in a SOHC VTEC VX motor into my friend 92 DX hatch. The car ran find if he accelerate gradually, but when he floor the gas, there is a lag(car feel like it held back for couple second) right when VTEC x-over point then pull hard after that point on. The ECU using on this motor is P28, and we also put a D16Z6 intake manifold. Anyone have an idea of how to solve this problem?

Thanks

 

the VX isnt' for acceleration
it's not even vtec, it's vtec-E.
it's for crazy gas milage.

if you want to solve this problem, swap it out, for a D16Z6

 

The VX D15Z1 vtec-e engine is nothing at all like the regular vtec D16Z6. The VX runs on only 1 intake valve until VTEC comes on, then it opens up the other one. Also the crossover point is near 3000rpm.

On the Z6 the crossover is around 4800 rpm but all 16 valves are working all the time, VTEC activates the high hp cam not just the extra valve. There really is no other ECU that can properly run a VX engine besides the stock one.

 

so the D15Z1 is nothing compare to the D16z6? how about if I swap the Z6 head on there?
Thanks

 

You're already running the P28 ECU. IMO, sell the D15Z1 motor and get yourself a D16Z6 motor and transmission.

 

You will have a large drop in compression if you just swap a Z6 head on there, also the possibility of valve-to-piston interference since the VX head has much smaller valves it's possible the reliefs in the pistons aren't large enough for the Z6 head either.

The Z6 in stock form is 125hp, the d15z1 is 92hp. That right there tells you how comparable they are...

 

This might sound dumb, but check the oil that happened in my car and it turned out I was about 2 quarts low cuz my drain plug wasn't on tight at all and was leaking slowly

 

vtec-e on a vx motor kicks in somewhere in the neightborhood of 2200RPM and d16z6 kickins at about 5000.
Besides the point that you run on 12 valves until 5000, your running on a map that is too rich for your car.
With the stock p07 ecu, your car would run PERFECT. I have confirmed this with a wideband, the afr curve was perfect as it gets.


PS. Many ricers on this board wiill occasionaly ask how to make it feel like vtec is kicking in harder, I'm saving this tread for those occasions.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by klungemonger &raquo;</TD></TR><TR><TD CLASS="quote">
On the Z6 the crossover is around 4800 rpm but all 16 valves are working all the time, VTEC activates the high hp cam not just the extra valve. There really is no other ECU that can properly run a VX engine besides the stock one.</TD></TR></TABLE>

Correct, a virgin p07 is the only ecu made for that motor; however, any obd1 ECU can be modded to have it run a p07 program. Why would you do this? It is better in the long run in the sence that most people need their car tuned, and a chipped ECU is the way to go IMO; for it is cheap and more then enough for many of us street car's.