Cinquecento/Seicento How to: MPI 8V and C526 Gearbox Swap

For the final page, I'll cover some aspects of further improving your little Cento.
Keep in mind that I've not (yet) done any of these except mapping the ECU. These are mostly from experience with my Puntos, as well as feedback from other Punto/Cinq/Sei owners. So I'll approach these in a theoretical way. A few searches around the forum will likely provide better insight about these improvements. Again, all of these are left at your discretion.

In Portugal, all kinds of modifications to cars are outlawed, and therefore illegal. The way we get around this limitation is to make everything as low profile as possible. This leaves room for many things to still be improved, as you may have seen from this tutorial.


First of all; I think it is important to make a point here, and say that, in practical terms, there is absolutely NO REASON why you shouldn't be getting the stock power from your engine. Even if you've got a full P60 engine with P866 cams, you would still be getting near the baseline 73hp. The plastic manifold and Sei throttle body are the same as in the Punto, and it's not that restrictive. Plus, some SPI Cinqs and Seis doing the bottom end swap only, have dyno'd over 80bhp with minor changes, and the SPI manifold is a lot more restrictive.

This leads us to out first real issue: Mapping the ECU.

Mapping the ECU will unlock the full potential of your engine. Even though the stock ECU can keep up with the new engine (albeit running roughly after a reset, and it will take some time to adapt), you would always be better off with a custom map: It would allow you to get even more power than what is rated for the donor engine, as well as fuel ecconomy and emissions.
To put it simple... You need to have someone map your ECU to the new engine. Or else all the work will be mostly in vain.


From there, you can either get a larger throttle body (adapting Punto 85 TBs with a spacer plate is not unheard of; and it's pin-compatible to the Sei loom) or have your own machined and enlarged. Again, you should map the ECU after doing changes to the throttle body, as this will change the volumetric efficiency of the engine.


The exhaust manifold is an awful design as well. There are "cheap" alternatives on ebay which will provide a decent performance boost, as well as time-proven parts from Supersprint and the more. It's your choice really. You shouldn't go for an exhaust system that is too large (definitely not over 50mm) or you'll lose top end performance. Also, don't buy manifolds fit for a 1.0/1.1 FIRE engine. Remember to buy the 1.2/1.4 manifolds, as these are taller and will clear under the sump with no modifications. One from a Punto MK2 60 will do (two Lambda fittings). The Punto stock one won't fit, so don't try. It must be an aftermarket one. A P75 manifold can be adapted as well.
There are two things I'd recommend you to do when fitting one of these:

1. Use insulating exhaust wrap to cover the manifold branches, and prevent them from burning other pipes.
2. Adapt the exhaust system (NOT the manifold) to make it fit. The manifold will likely be for a Punto or so, and it will have a flange. Since you'll likely be changing manifolds more often than the exhaust system, just adapt it to fit any manifold of the same design.

Keep in mind the reduced clearance between the slam bar and head.


The intake is one of the most easy to improve things in these cars. You will notice there's an empty space right above the gearbox, and in front of it there are direct openings to the outside on the bumper.
You can easily fit a boxed performance filter (like Green or BMC) in there and route the piping to the front.
I don't know if there are any pre-made kits that will fit an MPI sei. The most important thing is to get fresh air onto the engine here.
The TB outer diameter is 60mm.


For the last thing, you should definitely improve on your suspension and wheels.
I would say that even with a stock Cento, the worst part about it is the suspension, and the second one is the tire size. With an improved engine, you'll definitely need at least a 165-wide tire. I have 155/70 R13 tires and they simply cannot keep up. The last front set lasted only about 2000 miles
If possible, fit 175/50 R14 or 185/50 R14, which people seem to use often. The 175/50 R14 is the same size as fitted to the Sei Abarth.
I am also using TA Technix springs (those are rated 60/40) which add a bit of stiffness to your cento. They don't lower that much, and provide a good compromise between comfort and performance. Get better shocks too if yours feel sloppy around turns. Check the ARB bushes too!


Most importantly, have fun with your Cento! It means nothing to have the fastest, wildest car on your street, if you get no fun at all driving it! Consider that most mods approached in this guide will dynamically change your car, so don't do them if you don't feel like they're needed, or if you feel like they will hurt the fun factor of the car.





That's all guys! I hope this guide helps you, at least through some of the issues I've had on my own swap