69mm TB for reconditioned 3.8L

[Toms 50th Ani]

Over a year and a half ago, my VT's original motor died and I decided to get a replacement crate motor installed. All the bolt-on mods were transfered to the new reco motor (extractors, 1.97:1 FIT rockers, K&N filter, SS CAI, 81deg thermo) so since I got the car back, I have lost alot of low end torque. Power kicks in above 3000rpm, drives better when cold and boggs down when hot and lost fuel economy. I blame the low-end "lack of power" for lost fuel economy as to get the car moving, I really need to give it full throttle before the transmission drops back a gear ot two.

I've been thinking just recently, if a reconditioned motor has had it's cylinder bored out, oversized pistons/rings (and god knows what ever else), then wouldn't it want to suck up more air whilst accelerating compared to an original motor? If I have the bonnet up and rev the motor by the TB, I hear a giant gasp for air before the engine begins to revs from idle. I'm very sure my old motor didn't do this.

So the main question is - will a larger TB help the problem? At the moment, it feels like the engine is being starved of air before it hits the powerband of over 3000 rpm.

Tom

 

[Cashman_309]

May require a tune.

All this money spent on the motor but did u look at the gearbox at all?

 

[Toms 50th Ani]

transgo stage 2 shift-kit installed. transmission had a service a few months ago and the previous oil was very clean considering it was last serviced/opened when the kit was installed approx 2 to 3 years ago. Forgot to mention, I have a Dr-Bob memcal installed. I do have a stock chip which I tried and as expected, worse performance so the tuned chip was put back in. Oxygen sensors were replaced 2 months ago.

Going over the Gateway Bridge (brisbane), I manually drop it back to 3rd to keep the RPM around 3000 and it will accelerate up the bridge. Keeping it in drive with a little more throttle input at between 1700 and 2000 rpm and I'm loosing a lot of momentum.

Most of the driving is done between the 1500-2500 rpm range which is the flat spot (when hot). In effect, I'm pressing deeper on the accelerator and using more fuel so thats why I'm asking if the engine is starving of oxygen considering the oversized pistons in the reco motor? I'm still using the standard throttle body.

 

[wraith]

When a reco happen's there isn't that much material taken off. Have you got a tune to suit your mods. What fuel do you run?

 

[pjdm1980]

Have you done a code check?

 

[Munz]

I've been thinking just recently, if a reconditioned motor has had it's cylinder bored out, oversized pistons/rings (and god knows what ever else), then wouldn't it want to suck up more air whilst accelerating compared to an original motor? If I have the bonnet up and rev the motor by the TB, I hear a giant gasp for air before the engine begins to revs from idle. I'm very sure my old motor didn't do this.

Most reco motors would have done head gaskets (easy fix motors) as it wouldn't be viable for the reco company to be boring blocks and fitting larger pistons, those badly damaged motors would go to the metal recyclers.

Also you say it gasps for air, seems like it could be the manifold gaskets as air could entering through there rather than the throttle also check your manifold vacuum lines as well

 

[Toms 50th Ani]

The memcal was the last upgrade and was tuned for the mods. Fuel has always been 98 octane.

I'll ask my mate about the vacume line and gaskets. I'll try to get some recordings later.

Are reco motors ever the same?? I know I've lost bottom end torque and that I'm curtain of.

 

[wraith]

Ecotec already has a 65 mm throttle body so you won't notice too much difference. Sounds like some thing else to me.

 

[IBLOWN]

You do notice a little power up high and better throttle response with a 69mm but you also lose a little down low. Its not really worth how annoying the gearbox is when it changes way too early... Needs a tune afterwards.