Performance Mods

[jon8710]

Hi there 

After getting my car where I want it styling wise I’m looking at performance mods that can now be undertaken. The care has a 2 in 1 out Dansk stainless back box on it but apart from that it’s standard. 
What engine modifications are best to start on to increase BHP ? 
thanks

jon 
 

[Ian Comerford]

This all depends upon your budget.  I think the cheapest bang for your buck is still a set of SSIs and a decent back box.  After that it’s probably a set of ITBs which is quite a lot more than the SSIs.  You might also consider a new set of cams to work with the ITBs. It used to be that the best way to get more hp was to sell your engine and buy a 3.6 from either a 964 or 993. This boat has now sailed as they are a lot more expensive. How far do you want to go?

Of course the other way to get more performance is to remove some weight.

[sopor]

As the old adage goes… “Speed costs money. How fast to you want to go?”

As Ian has said there are few “cheap” external mods that will get you much.

Consider getting the suspension and steering checked and set up by someone like Center Gravity. Another favourite of mine is a good driver’s seat that holds you in place and lets you feel what the car is doing rather than where you’re expending effort holding yourself in place. 

[Phill]

What year is your car? Are you starting with 180, 188 or 204 hp? 
You say you have a 2 in 1 out backbox so assuming you already have SSIs or the Dansk equivalent? As said before, that is your biggest improvement possible externally without spending fortunes. 
Also assume your air injection pump is gone? 
I set about installing ITBs and EFI on my old car (now @gt two ) and that made a huge difference. I believe Lee is now getting 230hp? (The car is a 1978 with a starting point of 180hp). I did this on a budget using Triumph motorbike ITBS but it still worked out at 2.5k. New cams could easily up that hp some more.
And also, as stated above, weight loss and a good geo is a game changer, especially unsprung weight. When I fitted Boxster calipers the difference in steering weight was an eye opener. I stripped out a good 70 80 kg and Lee has gone even further. This is absolutely noticeable in acceleration and handling. I also had a proper geo and it transformed the car. 
Many people have done all these things so you are in good company but it does take big lumps of cash.

[Beaky]

Most covered above, I also digitised my intake and induction using a "Specialist Components" kit, a bit spendy but make for crisp and linear acceleration - you'll need something similar if you go ITB's.

If your base engine is in good condition, you'll be amazed how a good GEO set up, new tyres and some mild tuning can really make a difference.

 

 

[gt two]

As Phill mentioned lots you can do but definitely start with the basics.

 

Lots of well modified cars on here to take inspiration from.

 

My car is now 990kg with the latest addition of a lighter bonnet, and with 241bhp at the last dyno. I could go for cams to add a bit more but I reason that I love the way it drives and the torque in the way it’s setup now.

pic of the engine with ITBs and EFI that Phill mentions.

 

 

 

[Lesworth]

Echoing above but I would start with SSI's if not already on the car and a full suspension geo set up (another shout out for Centre Gravity).

Then I would go with a CDI+ box from Classic Retrofit.

I would avoid silly air filter type 'upgrades'.

[strosek34]

Mines a 3.4 with a few mods and weighs 1070 kg now, work I've carried out over the last 20 years,    these days mechanical work is so much more expensive  than it used to be so like others have suggested start off with as many weight saving mods as you can plus a good alignment setup by someone like Center Gravity and then see how it feels.

[jon8710]

15 hours ago, Phill said:

What year is your car? Are you starting with 180, 188 or 204 hp? 
You say you have a 2 in 1 out backbox so assuming you already have SSIs or the Dansk equivalent? As said before, that is your biggest improvement possible externally without spending fortunes. 
Also assume your air injection pump is gone? 
I set about installing ITBs and EFI on my old car (now @gt two ) and that made a huge difference. I believe Lee is now getting 230hp? (The car is a 1978 with a starting point of 180hp). I did this on a budget using Triumph motorbike ITBS but it still worked out at 2.5k. New cams could easily up that hp some more.
And also, as stated above, weight loss and a good geo is a game changer, especially unsprung weight. When I fitted Boxster calipers the difference in steering weight was an eye opener. I stripped out a good 70 80 kg and Lee has gone even further. This is absolutely noticeable in acceleration and handling. I also had a proper geo and it transformed the car. 
Many people have done all these things so you are in good company but it does take big lumps of cash.

mine is an 83 so around 200hp if I’m correct. 
No my car just has early model exhaust system on it but not SSI so it sounds like this will be my next mod at some point. 
 

Sounds like SSI is next on the list then, what kind of cost should I expect to swap them over? 
ITBs and cam work is a dream and one for the future as I’ve heard they are extremely expensive, where is good to start looking at such items? 
 

[Phill]

Have a look at Type911 for an idea on prices and speak to Matt.

There is a current thread here on ITBs.

 If you are handy with spanners it’s perfectly doable yourself, I did mine entirely myself and it’s fully documented in the fuel section.

 

Edited July 4, 2023 by Phill

[Lesworth]

11 hours ago, jon8710 said:

mine is an 83 so around 200hp if I’m correct. 
No my car just has early model exhaust system on it but not SSI so it sounds like this will be my next mod at some point. 

Stock 83 SC will be 204bhp but they tend to be a little more actually. With SSI's on my completely stock and healthy engine I got 231 but I don't know what it was before the SSI's so can't say how much of that is down to them versus the famous Porsche power understatement.

You'll be pleased I think. The improved sound is also worth it. I also put a Dansk sport 2 in one out rear box on it. Sounds good without droning and I can still hear the wireless.

This and the suspension set up, corner weighting etc are the best things I have done in 14 years of ownership.

Edited July 4, 2023 by Lesworth

[Bugs 77]

Yep all the above, getting suspension, brakes and transmission/shifter sorted makes a big difference to how the car feels and drives, the stock 3.0 ltr lump is pretty good when in shape.
But extra power comes from higher compression and better breathing, you're a little limited in upping the cams with the stock injection system hence changing to something like EFI & ITBs that are unaffected with hotter cams, I went down the carburetor road with PMOs for that reason and a very simple setup (but they can stink out the garage). I'm just on 250hp.

Where it breathes out.

[sopor]

You’ll soon be on nil bhp unless you connect that oil line. 😉

Looks lovely and tidy and clean. 👍