Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Plus 4 GDI Aero Racing Manifold & Exhaust Upgrade

This upgrade has been in planning for a while. My GDI is now three years old, and my only "complaint" has been the super sensitive throttle. I had the opportunity for an ECU flash over in the first six months, but after discussion, left it alone. I've never felt the "flat spot" around 3,000 rpm, but I've had low mpg and a very black exhaust from day 1.

Having said that, it passed the MOT recently on emissions with no problem.

A couple of weeks ago I picked up the full Aero Racing system from the factory, and over the last three days have fitted it and the car is running. I plan to take it out on the road tomorrow, and all being well, I'll take it back to the factory for the Club-sport ECU flash, which brings the power up to around 180bhp.

An owner who has done this conversion e-mailed me with his story, and I also spoke to the Cainmeister as to what to expect. Both were spot on. The GDI manifold won't simply lift out, and the new manifold requires a few mm removing from the inner wing valance for clearance.

I did suffer further complications, especially with my front offside mudflap, which needed significant modification to clear the twin pipes which come through the inner wing valence, then turn 90 degrees just behind the mudflap. In addition I had made a heat shield for the GDI exhaust, which no longer fits, and so I had to make up a new one.

I've taken a lot of photographs, and will post the story as soon as I can, hopefully after tomorrow's road test. The engine already feels more eager, so I'm looking forward to seeing how it performs!

Hi Dave

Thanks for the update, It'll be interesting to hear your thoughts on the performance and also the change in tone.

I'm interested why you opted out of the ECU flash - Mine is booked in soon to hopefully eliminate the flat spot with my car.

PM Sent also.

Cheers and I hope it offers the extra performance

The system seems to be similar, but not the same, as the Plus 4 SS system as fitted to my car. The distance from the engine to the catalytic converter is quite long and there were always problems getting the cat up to temperature and functioning correctly. With the original map I was always getting the engine warning light come on and MOT tests could have been a problem. In part this was resolved by fitting exhaust wrap but it was not really resolved until I fitted the throttle bodies and was able to fine tune the map. Not an option that you have with the GDI engine.

The other issue I had was that after 60,000 km the cat started to fail and I had exhaust smell coming into the cockpit. This was resolved by fitting a new larger diameter 300 cell cat. The sound was muted slightly, particularly at "around town" throttle levels, and the tone deepened a little. The cat manufacturer said that the size of the cat that Morgan had used they would normally recommend for no more than a 1600cc engine.

I suspect that other than the need to correct fuelling and emissions you will need the new flash to avoid constantly getting engine warning lights from the O2 sensor downstream of the cat.

No warning light yet on mine. I have just lent it to a friend of mine who has a P4 Duratec and he was impressed.

More bhp , more torque , more sound , its a drug !

So let the story begin..........

First I removed the exhaust system. Because I treat my exhaust mountings as a service item, and restore them every year or so, it only took a few minutes to remove the exhaust. For the refit, I had bought new bobbins and stainless U bolts. A couple of the bobbins had the studs turning in the metal discs.

I then removed the sensors. They are not the same. Usually I have trouble with latched electrical plugs, but these were easy. A simple thumb press and they slid apart.

Here's a funny thing........the upstream sensor which I removed was a light matt grey, like an old leaded fuel tailpipe.

The downstream sensor, after the cat was covered in black sooty deposits..........I just can't understand what's going on with that.

The leads need extending and I got these from the factory. Upstream, and downstream.........





To remove the manifold and cat, the engine needs to be lower. One option is to remove the cam cover, but I'd rather not do this. I removed the offside engine mounting, and lowered the engine as far as I could, but it wasn't enough, and there's a risk of damaging other things. So out came the hacksaw, and I cut the system in half just below the cat. Then it lifted out!



At this stage I wrapped the manifold, but I don't like the look, and the next day I took it off.....just a personal thing. The shiny pipes look so much nicer. The manifold gasket is shim steel, and I reckoned I could reuse this, which I did. The new manifold bolts on easily with five nuts.





These are the sensor plugs in the engine bay.



I also found that the underwing protector was hanging off......just on this side, so I pulled it off, and replaced with Reflect-a-cool.

This is the remains:



What I pulled off:



And as replaced:



To be continued....................

The next image shows how the manifold passes through the inner wing valance.....At the top it was necessary to trim a few mm for clearance.

I'd removed the wing stays to get more room to remove the original manifold, but it didn't help.

The large hole in the valance to the left of the pipes, I've closed off with an aluminium plate.



This is the next section down to the cat and as you can see, is way too close to my mudflap and brackets.



This is how the cat sits. I'd previously applied reflective insulation to the fuel pipes front to rear.



The new sensors went in easily and the next stage is basic nuts and bolts.





This image shows the rear twin tailpipe. The L shaped bracket is slotted and so the tailpipe rests in a shallow bobbin, which rests on a new stronger exhaust bracket. Obviously to fit this entails removing the luggage rack and spare wheel!

Fitting the bobbin is best described as "fiddly". This bobbin doesn't come with washers and nuts. But I have a shelf crammed with such indispensables.



You might think it's all over at this stage..............



But my exhaust assembly paste was going off, and I had to reconfigure the mudflaps.......and replace my engine heat shield which no longer fitted.........

To be continued.................

So..........

The rear mudflap mod was a simple cut......

For the front I had to extend the inner bracket, and then strip the mudflap, cut for clearance and add an aluminium curved panel. I used my redundant engine heat shield for this.







Things are quite tight around the back and here you can also see my closure plate.



I also made some new exhaust skid plates. Each time I do this they get bigger, but it does keep the road crud off the mountings.





This is the engine bay before I fitted the new heat shield............



And finally, when everything was done..........






In the garage, the engine fired up first time and sounded much less throttled. It revved freely, and the noise is little different to the standard set up.

Today after a fifteen mile shakedown........no knocks or rattles, a nice throaty roar under acceleration. Smooth idle. Much freer revving through the gears, and most noticeably, more bottom end torque, easily pulling away in higher gears than before. And it feels a bit quicker. Whatever ....it's a chalk and cheese transformation.

So far no engine light! The new cat doesn't come with a jacket, so I've wrapped it in a weave blanket, and put the old cat cover over the top. If I get any problems with the cat not running hot enough, then I may have to rethink the manifold wrap. My heat shield prevents the hot air rising and enveloping the cold air intake, and should also keep the manifold hotter. The mudflap also shields the cat from air flowing under the Morgan. Interestingly the offside wing now gets very hot. I added a blanket to the cat on my 4/4 Anniversary because the wing was getting super hot, but even with the double layered insulation.......that wing is hot!

So, my next step is the trip to the factory and the ECU flash. It will be a week or so, and I'd like a bit more road time to get to know the characteristics............

Amazing attention to detail Dave..you should write a book !!!


You lucky man having three Morgans in your garage !!!

I would certainly like to talk to you at somepoint Dave once the flash has been done to get your thoughts on your new setup versus my Librands manifold setup etc!

Looks very well done (as ever!)