2.7RS MFI setup on a 3.0L?

[GrantG]

I have a hot 2.7RS MFI motor (235hp on engine dyno at sea level) with a pump (019 specs) built by Gus at Pacific FI and plastic stacks that have been opened up slightly.

I broke a crankshaft on that motor (Mag case), so I'd like to build a new motor on a 3.0SC case.

I was thinking of going 3.2SS twin-plug with PMO carbs, but I would really rather retain MFI if possible.

I spoke to Gus today and he said the factory made a few 3.0 MFI cars (not RSR) that used the 2.7RS MFI equipment (same space cam, etc.) and S cams.

So, has anyone built a 3.0MFI like this? I was thinking that I might be able to keep my stacks and pump unmodified and make some new S cams that would fit an SC case, since I live at high altitude (5,000ft minimum) where the extra displacement will be offset by the thinner air (hopefully the stacks and SSI's should flow enough air up here where we lose 15-20% HP from sea level).

Any thoughts? Would using 98mm pistons (3.2SS) work even better or would the volumetric efficiency start to diverge more from the characteristics of the MFI setup?

Would increasing the compression come without complications (i.e. 10.5:1 twin plug, while I had 9.5:1 single plug before)?

Anything to watch with respect to heads and port sizes?

Much appreciated,
Grant

[Flieger]

Well, living at high altitude means you should be able to run higher compression but might need to be careful if you come back down to earth.

I would try to get the Supertech Supercrank and make a 2,8 short stroke and use the same MFI. Mark Jung would be a good one to consult with on space cam and fuel piston modifications.

[Walko]

Hi Grant
I built a 3.2ss with mfi.
To answer your question an s cam on this type of motor is quite a mild cam in view of the extra displacement.
The only difference I had was I used mag stacks and throttle bodies opened up by Matt at eurometrix to be the same size as large port sc heads.
The mfi injection used a stock 019 pump and the biggest problem we had was it tended to run a bit rich. I had the pump rebuilt in Europe to stock specs.
Pistons were max moritix to start with and when I chased more hp we went with JE 10.5 .1 the motor was single plug and made 305fwhp.
Fuel consumption sucked but the car with a short ratio box was crazy quick up to 200
Kms.
These motors will rev and heaps of fun.
Michael

[GrantG]

Thanks, Michael. Did you feel the piston change was worthwhile? Do you think a more aggressive cam than an S could've been made to work with the 019 pump (2.7RS Space Cam)?

Were you running rich at the top rpms or midrange?

Sounds like a fun ride (I have short gears too)!

[Walko]

Grant,

The piston change was worth every cent they cost.

I think that going to an RSR spec cam would have seen more power however I think it may have resulted in a motor that may not be as responsive low down.

The car was running rich up high. Mind you it wasn't running so rich that we were worried about washing bores or causing damage.

Michael

[atelier14]

Originally Posted by Walko

Hi Grant
I built a 3.2ss with mfi.
To answer your question an s cam on this type of motor is quite a mild cam in view of the extra displacement.
The only difference I had was I used mag stacks and throttle bodies opened up by Matt at eurometrix to be the same size as large port sc heads.
The mfi injection used a stock 019 pump and the biggest problem we had was it tended to run a bit rich. I had the pump rebuilt in Europe to stock specs.
Pistons were max moritix to start with and when I chased more hp we went with JE 10.5 .1 the motor was single plug and made 305fwhp.
Fuel consumption sucked but the car with a short ratio box was crazy quick up to 200
Kms.
These motors will rev and heaps of fun.
Michael

Hi Michael,

Your 3,2SS was running rich with an S-cam, openend mag throttles & stacks (to 39mm I assume) and the 2.7L RS space cam in a stock 019 pump - that's astonishing. Could you indicate where in Europe you had your pump rebuilt?

Regards,
Christian

[GrantG]

Originally Posted by Walko

Grant,

The piston change was worth every cent they cost.

I think that going to an RSR spec cam would have seen more power however I think it may have resulted in a motor that may not be as responsive low down.

The car was running rich up high. Mind you it wasn't running so rich that we were worried about washing bores or causing damage.

Michael

Thanks, Michael. Which heads were you using (and additional porting done)?

[Henry Schmidt]

We have been running a modified 060 space cam in all of our big bore MFI engines.
Remembering that these MFI systems are stone age technology and the map will never be perfect, with time and patience you can get them pretty close.
The key to finding a drivable compromise is building a complete package that includes an appropriate header (heater box) and muffler.
More than one mechanic has pulled his hair out trying to tune an MFI engine with an inappropriate muffler.
Here is the 3.2 SS we build for Scott Longballa.

[Walko]

Christian
The pump was rebuilt by Autofarm ( I assume a subcontractor)

We did discover a huge difference in the modern fuels. Our research revealed the density of modern fuels has changed substantially since these motors wwre originally built and that each manufacturers fuel density is different and this seemed to have a marked difference on the tuning.

Michael

Michael

[917guy]

I am reading all this with interest. I have been using 2L and 2.4L S MFI pumps on a 3 liter with early S cams, but am not settled on what fuel system to use in 2012. EFI is still a temptation.

The density is a modern issue. E10 and pentane content can getcha. On a couple of highway trips in 2011, I used my 1985 5 liter Capri (OEM Holley 4 barrel) and its ability to idle is dependent on fuel brand and density. Great one tank, terrible the next, on long prairie trips, where product varies by county. It is my hope that density is more a carb thing than with MFI. The magic with EFI is that it adjusts more completely and seemlessly for unanticipated density and BTU/pound changes.

David

[GrantG]

Originally Posted by 917guy

I am reading all this with interest. I have been using 2L and 2.4L S MFI pumps on a 3 liter with early S cams, but am not settled on what fuel system to use in 2012. EFI is still a temptation.

The density is a modern issue. E10 and pentane content can getcha. On a couple of highway trips in 2011, I used my 1985 5 liter Capri (OEM Holley 4 barrel) and its ability to idle is dependent on fuel brand and density. Great one tank, terrible the next, on long prairie trips, where product varies by county. It is my hope that density is more a carb thing than with MFI. The magic with EFI is that it adjusts more completely and seemlessly for unanticipated density and BTU/pound changes.

David

Do most here use MAP or some other sensor with EFI that will adjust for fuel differences? I was thinking most aftermarket EFI setups just used a throttle position sensor, crank sensor, synch sensor (to determine compression or exhaust cycle), temp sensors and barometric pressure sensors.