I just recently witnessed a dyno that has me scratching my head. The motor is a solid roller 383 Lt1 that made slightly Less power with a single plane mod (elbow and 58mm tb) than with a stock port matched LT1 intake. Part of the problem was the wideband indicated a rich (10.8 at 5000 to 11.8 at 6800) condition. The tune was the same that was used with the stock intake which had a perfect a/f ratio all the way through. We were all set to see lean numbers given the fact that the single plane would flow more air. Has anyone else experienced this phenom? Obviously a tune will fix this but I want to know why it is so rich now. I don't know what the map readings were during the pull.

 

My guess is velocity has slowed, and you're not filling the cylinder with as much air as before.

How well matched are the intake ports to the head ports? If the intake ports are bigger than the head ports, you're introducing a lot of turbulence. Otherwise I'd say you have too big of runner volume for the amount of air you need to flow.

Just my scientific wild *** guess.

 

the LT1 intake is very inbalanced as far as air distrabution go's with the TB in the front and all the ports hanging behind that... so to speak.
Using the tune from a LT1 type intake on a single plan is going to kill power, it has no other choice when you look at the "injector balance tables" and see what GM had to do to make fuel delivery consistant from port to port. With a single plane you have a balanced intake so you need to do major work on a couple of fuel tables to see the results. My best sugestion would be find another dyno shop/ tuner that can make the corrections to the ecm then do your pulls and tune from that point and not just take your buddys money for disapointing dyno pulls. Why would any good shop use the ecm tunning from the previous stock intake set up reguardless of "solid roller this or cubic inch that" on a single plan conversition.... just kills me
...sorry about my being to the point here but you asked

 

What kind of power did it make with the ported factory intake??
What was the DC and SC??

 

Thanks, I'll let him know about those. All of his plugs however did indicate a rich condition. They were all pretty uniform looking. The power before the intake swap was 461 converter locked. After was 448. SC is 12.4. Peak power at 6100.

 

How's the drivability with it? Does the elbow and 58mm tb combo keep it from having the tip-in problems others have had with the big Accufabs?

 

Drivability seems good, and it idles good too. The throttle response is great, and the power curve is almost a shadow just slightly less of the stock intake. This is not a car that sees much street use. I'm not aware of any tip in issues.

 

what does the rest of the curve look like? torque? the rest did drop significantly right? not just by like a few hp? cuz if it's just a little lower that's not right

the way i figure it is that your not keeping good air fuel mixture, the non port matched manifolds are inducing a restriction at high rpm, or you really need a tune, and a single plane manifold is going to be completely different for fuel requirements than a stock manifold, so i'd look to get it powertuned on a dyno to see what it needs exactly

single planes build more power from like 4500 up the rest will be lower, so something besides the manifold changed, the rich condition might be a sign of a sensor being out, those new motors should control the a/f ratio i thought though?

 

The manifold was port matched and drilled to bolt on the LT1. It's a Team G converted over. The converter flashes to 4800 so there is no info below that.

 

Hold on here....

The motor is making the same power now with the mixture being richer, but the same amount of fuel is being added. Sounds like you just picked up the BSFC numbers of the motor, making more HP per lb of fuel. Now giving the motor less fuel and it makes more power potentially then the BSFC numbers will be much much better now.

You are probably feeding the cylinder with as much or the same amount of air to get the same power.

You have to realize on a LT1 intake the front 4 cylinders are lean while the rear 4 are rich, and you come up with a 12.8:1 A/F ratio. All 4 cylinders aren't that ratio. A single plane has a better chance of those all being the same ratio.

Bret

 

That may be the problem. The single plane doesn't show any gains over the LTx until over 6200. If the hp peak was around 6600, you'd pick up power.

Mike

 

I thought it was supposed to impove the power band around 4000 and up??

 

Do a search for the username Turbo6 on LS1tech. He's done the best before/after comparison I've seen on this. He posted dyno results of a 396, AFR220's, and large solid roller (255+) using an LT4 intake and a single plane. He lost power below 5200, broke even 5200-6200, and gained from 6200 on up. His peak rose by about 15 hp.

Mike

 

mike

you sure thats his name"Turbo6 "??

I just searched every post of his, and nothing about single plane 396's.

You got a direct link?

 

Mike, I think your missing chrism400's question. He didn't question the power, he's asking why the engine when rich with the swap.