Series 2 Backbox on Series 1 - Will It Damage The Motor?

[StinkyDogFarts]

Hi All,

I'm replacing my stock headers on my Evora S to mainly help reduce engine bay heat, but also to reduce some weight and gain a little bit of performance. I'll add a sports cat in the midpipe/linkpipe position, sized at 2.5 inches to maintain OEM sizing.

I've run across a couple aftermarket Ti backboxes that are sized for the Series 2 Evoras (3 inch main pipe, with I'm guessing close to the OEM 1.875 inch by pass into the muffler). I know it's physically possible to install these on the earlier series (Evora or Exige) by either replacing everything from the y-pipe/downpipe back, or using a midpipe/link pipe adapted to 3 inches / 76 mm at the connection to the backbox, and I've read of a few owners that have said they've done so on TLF's (mainly on Exiges though).

My thoughts on doing this are that 1) the Ti will provide substantial weight savings over the stock backbox, and even decent weight savings over a SS Larini or 2bular, 2) with only one 200 cpsi sports cat, the volume will be a lot louder than stock, and for daily driving around town, which I do a lot of, the valve closed routing through the 1.875 inch tubing will help lower the sound some, much like Lotus decided to do for the 400 to meet the drive by test, and 3) a hopefully somewhat better/louder sound at high rev canyon driving when the valve is open and the exhaust is flowing through the 3 inch portion.

What I haven't been able to figure out is, is this "safe" for the series 1 motor? I'm guessing yes, since all the Series 2 cars force their exhaust through the 1.875 inch pipe when in standard mode and low rev driving (and even the Series 1's force the exhaust through a 2.125 inch internal pipe inside the stock backbox), but maybe there is something in the Series 2 factory tunes to account for this? Would this change be within the range that a series 1 ECU could self adapt, or would a re-tune be needed? I plan on getting a tune (Inokinetic from the US) and will ask this same question to them to see their thoughts, but figured I'd ask here first.

I know 2bular claims a 40bhp loss on the 400 with the valve open. I only saw a dyno that showed a 5 bph difference between a 2.75 and 3 inch backbox, but maybe that was before the ECU self adjusted. A 40 bhp loss would probably not be worth it (if true), but for only a few horsepower loss, I'd be willing to do this, for the reasons stated above, assuming I won't blow up my engine (eek).

Any insight is greatly appreciated!!!

Edited March 4, 2022 by StinkyDogFarts

[Alfa2Evora]

I think 2bular quote a 40bhp loss on the 400 with the valve open on the factory exhaust, due to the drop in boost, but this is 'cured' with their system. Don't know how the Ti backbox compares in all this but I'd imagine it'll be much the same as the 2bular.