Gutting the secondaries - a tip

Contour Enthusiasts Group Archives

I have just removed the secondary butterflies and shafts from my SVT LIM and thought I would pass on a little tip.

After removing everything, just plug the holes left by the shafts with metal-loaded epoxy. It sets very quickly and can then be smoothed to a polished finish with a Dremel & fine stainless brush running at high speed. You wont harm the bores if you just use gentle pressure. The result is twelve nice smooth bores with absolutely no obstruction to restrict airflow.

I didn't bother to plug the holes between the twin ports of each cylinder because there won't be any differences in flow or pressure. I also epoxied a couple of M8 bolts in the shaft exit holes to tidy things up, and then removed the secondary actuating box & cable.

Just need my mapping session now to finish the job

Why are you removing the secondaries?

Mark

I am in the process of finishing my mid engined project. My car only weighs 700Kg so any loss of low down torque is not an issue. I have gutted the secondaries to get a little more airflow, along with SVT upper & lower inlet manifolds,MBE ECU, custom made exhaust, 10mm ignition leads and induction kit. A mapping session will get everything back on track and I estimate that 220bhp should be easily achieved (300 with a whiff of NO2

)

Should make an interesting power / weight ratio

Are you talking about a noble? that's the only light Duratec MR car I know of...

It is vaguely similar although mine is NA for the time being - I am looking at supercharging some time next year after I have proved everything holds together.

It has been compared to an Ultima (although a bit smaller and more affordable) in the past which I regard as a compliment. It has a novel design with two-part doors which are removeable for summer driving.

Originally posted by RazMan:
It is vaguely similar although mine is NA for the time being - I am looking at supercharging some time next year after I have proved everything holds together.

It has been compared to an Ultima (although a bit smaller and more affordable) in the past which I regard as a compliment. It has a novel design with two-part doors which are removeable for summer driving.

pics?

Mark

Here is a little preview to give you an idea..

Since this pic was taken I have revised the doors - the window section is 'gull wing' and the lower section is 'scissor action'

Wow, I can't say I've ever seen one of those before. It looks pretty small! Should be pretty fun when you're all done.

Mark

I want one....BAD!

So where did you get the body from?

The car started out as a kit from http://www.aeonsportscars.com but I have modified just about everything to my way of thinking. The original chassis was a three seater but I wanted a conventional two seater because I needed a little more space (I'm a big fellah

) so a central tunnel was installed which now houses all of the services from front to back.

I've got Wilwood 4 pots on vented discs up front with Sierra brakes and discs bringing up the rear.

I wasn't happy with the original bodywork so I redesigned just about every body panel and got moulds made. The front now uses BMW Mini headlights and indicators. The rear uses Alfa Romeo 156 lights, but in the Lexus style.

The interior is quite high tech with an Evodash for all the instruments and remote door poppers to open the doors (no handles at all) There are 90 led's scattered around the interior which gives the car an eerie blue glow at night. The only conventional bulbs in the car are the headlights (which are HID units) - even the reversing lights are led's.

Correct link http://www.aeonsportscars.com/

GT3Coupe is nice! Very Noble like. $18,190 for the kit to build yourself or 32,648 for a turn key. What is shipping to the US for just the kit?

Originally posted by RazMan:
I didn't bother to plug the holes between the twin ports of each cylinder because there won't be any differences in flow or pressure.

That is incorrect. The pressure generated by the different UIM port lengths (and thus different air speed & density respectively) does create an imbalance/bleed through.

All the other information has been online for 5 years or so but that was a nice refresher.

Ok maybe I oversimplified things but the small differences shouldn't affect power output to any measureable degree, especially as I am remapping the ecu to compensate.

I will probably junk the UIM & LIM later anyway and convert to Triumph Triple TBs with short trumpet intakes - but this will involve some bodywork mods and possibly some head work.

Gutting the secondaries.

I got a tip --- Don't DO IT!

If you do a full 3L swap with 3L manifolds then do it IF you can correctly tune them.
but you are asking for issues if you just gut them on a normal 2.5L.

Besides, they are only there to improve low-end torque.

As I've already said, any loss of low end torque is not an issue as my car only weighs 700kg - it is going to give me 0-60 in around 3 seconds in its present state of tune and mid-top end is more useful on the track! I have lightened the flywheel to make it rev a little quicker too. Also I am mapping it with an MBE ECU so any mods will be compensated for.

The secondaries are quite restrictive in their natural form (and the shafts don't help matters either)and I found that on the track, the transition from 6-12 bores was a bit messy (powerwise) and pinning them open improved things a little, allowing a smoother power curve. Therefore removing all restrictions should logically make things even better. It will also prevent the carbon build up on the secondary butterflies which is a common problem on these engines.

Originally posted by RazMan:
As I've already said, any loss of low end torque is not an issue as my car only weighs 700kg - it is going to give me 0-60 in around 3 seconds in its present state of tune and mid-top end is more useful on the track! I have lightened the flywheel to make it rev a little quicker too. Also I am mapping it with an MBE ECU so any mods will be compensated for.

The secondaries are quite restrictive in their natural form (and the shafts don't help matters either)and I found that on the track, the transition from 6-12 bores was a bit messy (powerwise) and pinning them open improved things a little, allowing a smoother power curve. Therefore removing all restrictions should logically make things even better. It will also prevent the carbon build up on the secondary butterflies which is a common problem on these engines.

Okay, I guess in your case you have a valid point and a plan. You wouldn't fit in the normal category of people who try and gut them as a sole means of gaining more power.

I agree War, his circumstances are different than 99% of anyone else contemplating doing this.

For anyone that comes across this later, removing the secondaries is silly if the engine is still in a contique!