Home built Hot Rod

[clutch-monkey]

My 3.6 is 11.3 and is absolutely fine.

my mechanic said he went to 11.5 and regrets it. He may have to run e85

[Coastr]

Will it have knock sensors with the Efi?

[MFX]

2 hours ago, Coastr said:

Will it have knock sensors with the Efi?

I am not sure the exact set up at this stage, but that is what I am thinking.

[Mike D'Silva]

On 07/02/2019 at 14:21, clutch-monkey said:

My 3.6 is 11.3 and is absolutely fine.

my mechanic said he went to 11.5 and regrets it. He may have to run e85

Is the 3.6 twin plugged?

Jeff

do you think you will see your motor this year?

[clutch-monkey]

6 minutes ago, Mike D'Silva said:

Is the 3.6 twin plugged?

Jeff

do you think you will see your motor this year?

yep
it's been no drama to run, similar to my stockish 3.6

[Mike D'Silva]

1 minute ago, clutch-monkey said:

yep
it's been no drama to run, similar to my stockish 3.6

From what I've garnered over the last several months, 10.2 is about the limit for single plugging. After that, they reckon you run out of safety in case of poor fuel etc.. and would risk detonation. I wanted to go 10.5 but was strongly advised against it by my American friend. The locals didn't seem to have an opinion.

Pretty sure stock 964 is 11.3 anyway?? 

I kinda feel sorry for Jeff with no motor at all at the moment. Jeff, if you find an old 3.0, did you want to send it up to get a quick refresh by me, then we can at least get you running so you can sort out suspension tuning etc?

 

[Coastr]

His original engine is a 2.7 so I’m guessing a ‘temp’ 3.0 would end up pretty permanent?

[clutch-monkey]

5 hours ago, Mike D'Silva said:

From what I've garnered over the last several months, 10.2 is about the limit for single plugging. After that, they reckon you run out of safety in case of poor fuel etc.. and would risk detonation. I wanted to go 10.5 but was strongly advised against it by my American friend. The locals didn't seem to have an opinion.

Pretty sure stock 964 is 11.3 anyway?? 

I kinda feel sorry for Jeff with no motor at all at the moment. Jeff, if you find an old 3.0, did you want to send it up to get a quick refresh by me, then we can at least get you running so you can sort out suspension tuning etc?

 

Ah I thought 964 motors were a bit less for some reason, yeah 11.5 is where it starts to get a bit cranky to run on regular fuel apparently. 

[MFX]

6 hours ago, Mike D'Silva said:

From what I've garnered over the last several months, 10.2 is about the limit for single plugging. After that, they reckon you run out of safety in case of poor fuel etc.. and would risk detonation. I wanted to go 10.5 but was strongly advised against it by my American friend. The locals didn't seem to have an opinion.

Pretty sure stock 964 is 11.3 anyway?? 

I kinda feel sorry for Jeff with no motor at all at the moment. Jeff, if you find an old 3.0, did you want to send it up to get a quick refresh by me, then we can at least get you running so you can sort out suspension tuning etc?

 

Haha, old 911 engines are cheap and easy to find everywhere  

Neil is actually packing my engine up this week, so it should be back here soon (I hope, but I will believe it when it gets here  ).

The final comp of the engine is 11.6:1, but he is sending it with base gaskets in .25, .5 and 1.0mm which can take it down to 10.6:1. I am not sure, but I will probably set it up to 11.1, just to be on the safer side, although Neil is confident it will be fine at 11.6. 

[Mike D'Silva]

But with all the different base cylinder gaskets, you will end up with a different deck height in each case too?

[Raven]

You will get away with 10.5 ,,11.1 on 98 octane ...both 964 and 993    3.6 engines were 11.3  from factory 

[Peter M]

2 hours ago, Raven said:

You will get away with 10.5 ,,11.1 on 98 octane ...both 964 and 993    3.6 engines were 11.3  from factory 

Not quite.  Whilst the 964's and 993's may have been advertised as having 11.3:1 compression ratios, I understand they measure out at around 10.5:1 in reality.

Also remember that they were also equipped with knock sensors as well.

[Peter M]

9 hours ago, Mike D'Silva said:

But with all the different base cylinder gaskets, you will end up with a different deck height in each case too?

Yes, which then effects the squish clearance which effects the effectiveness of the squish band which then has a significant effect on the chamber's susceptibility to detonation itself.

It's better to get the squish clearance right via the deck height and then adjust the compression ratio by machining the piston dome if need be.

Also we have been talking static compression which doesn't consider the effect of the valve timing.  ie.  If the value timing is really conservative it's possible the dynamic compression ratio will be close to the static but it's likely the cam Jeff will be using will have late intake closing so that will limit the actual compression the engine will see as the valve will be still open at the beginning of the compression stroke. 

[Mike D'Silva]

40 minutes ago, Peter M said:

Not quite.  Whilst the 964's and 993's may have been advertised as having 11.3:1 compression ratios, I understand they measure out at around 10.5:1 in reality.

Also remember that they were also equipped with knock sensors as well.

I have heard that too. 

[dobbo]

  Wouldn't different thickness base gaskets alter cam timing?

[Peter M]

Since the cam timing is set after the cylinders are installed its not an issue. 

[MFX]

54 minutes ago, Peter M said:

Since the cam timing is set after the cylinders are installed its not an issue. 

Exactly what I was about to say  

[dobbo]

Are the cam drive sprockets adjustable , slotted holes for the mounting bolts?

[Peter M]

Adjustable through a vernier arrangement of holes and one pin