Has any seen a power loss with a cut out open?

I had an electric cut out installed on my 98 SS a couple weeks ago. We did a run with it open after the retune and final adjustments today and I lost 77hp on the first pull and 50-something on the second, closed it and put down 392.
I was hoping to break 400rwhp but it didn't happen. My dyno back in april was 396rwhp. I guess it wasn't bad considering the temp was showing 104 in the shop and I am now putting the power down through an M9" rather than the factory 10 bolt it.

 

On my bone stock z28 I had stock manifolds crap stock everything with a drop in k@n filter and free mods , I ran a 14.1 then got a cutout and a 2800 stall , with the cutout open and nearly same air I ran a 14.1 put the cap back on ran a 14.08 . I believe cutout's benefit when you have headers just my two cents.

 

where did you put the cutout. No way in hell did the cutout make you lose 77hp

 

thats exactly what I was thinking..

 

Yea something is most definitely fishy here.......77hp?!!?!!?

 

I have slp headers, long tubes, and flowmaster catback.

 

I had the cut out put at the hump by the rear passenger seat. Absolutely nothing was changed between a 313 run and a 390 run except opening it. 3rd run with it open was 358 then closing on the 4th run to get 392. Everyone in the shop was in shock because we hadn't seen that before. A buddy running true duals with bullets opened his cut outs and gained 15hp on the same dyno.

 

I picked up 44rwhp when I open my cutout.

 

It's rediculous because I have been all over the net and have not found anything else realated to this. Everyone has something of a hp gain. I was hoping if nothing else it would at least get me over 400rwhp.

 

I would have to say there is something wrong somewhere, not exactly sure where, whether it on your car or on the dyno. I say this cause you did 2 runs with the cutout opened and didnt change a thing but gained 27 hp from your first run.. It's crazy, cause it's acting more like its choking out your car instead of freeing up exhaust.

 

leave it closed

 

I'm assuming something is wrong with the cutout itself or it wasn't installed correctly.

Instead of opening up and freeing exhaust it's probably restricting it considerably. I've seen people lose a few hp with a cutout open (due to loss of backpressure or something), but never 77hp. That right there just screams something is wrong with the cutout itself.

Have you looked at it and make sure it opens up correctly and that it's not blocking anything?

 

Yes I have looked it over and it opens all the way like it should. Its a 3.5 QTP and its weld on in a straight section so there isn't really anything to block it.

 

Its most likely the weather mainly for the dramatic loss. However, even the heat doesnt add up to that much power.

 

Were you getting knock retard during the run with the cutout open?

 

there is something wrong with the tune or something, there is no reasonw hy getting more exhaust flow would cause a power loss like that.

 

I haven't really drove it but a mile or so since I got it home. I hauled it to the shop and back on a trailer. I'm going to get it out this weekend and see how it does out on some back roads. I may go have it retuned once the temp cools down.

 

I was getting it when we first started tuning it but it cleared up.

 

How close is it to your o2is it tuned closed loop? Have you monitored stft with it opened compared to closed

 

This should be interesting when you find out what's wrong.

That's an insane amount of power lose. That's like doing a H/C swap and then going back to stock.