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Cam specs for turbo ? 

 

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 Post subject: Cam specs for turbo ?
Posted: Wed Jan 12, 2005 1:05 am 
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Hi Guys,

Can anyone give me an idea of what cam specs would be good for a mild turbo I6 crossflow 250 with a VL type T3.

I have looked at a few cam websites like crow, wade etc, and no-one seems to list anything regarding turbos (Obviously because they're not common).

Would a stock high torque cam be better then a 25/65 for example.
I know the turbos going to do most of the work, but if i am going to replace the cam during rebuild, i may as well put one in thats suitable.

The XF's an auto too.

I always thought that minimal overlap is best for turbos am I right ?
If so this means small cam ?

Thanks

Mike
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Posted: Wed Jan 12, 2005 1:16 am 
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Be wary of any cams that are used with blowers ..Turbo's have pressure in exhaust approx twice the boost level. So a reverse cam with specs on exhaust valve closing early like 224 inlet and 218 exhaust 114 + lob centre and 110* intake centreline......With little or NO overlap....

You will need a custom ground cam though....
Talk to Jamie Farmer at Cylinder Heads Dynamic...
He has built some tuff 6 cyl turbo Fords....

 

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Posted: Wed Jan 12, 2005 7:35 pm 
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yeh a custom grind cam is the way to go, i went a custom grind in mine, i havent run the engine yet, but with the specs its got it should be perfect

 

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Posted: Wed Jan 12, 2005 8:27 pm 
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EBXR8380 wrote:
With little or NO overlap


.....At 050" duration. Its virtually impossible to have zero overlap at advertised duration. Also you want an instense profile, the smallest adv duration possible for the 050" duration you want with as much lift possible. These newer style cams have better idle vaccum and broader rpm range than their dinosaur equivilents.
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 Post subject: turbo cam
Posted: Wed Jan 12, 2005 8:49 pm 
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Hi all
Im running a towing cam which gives me lots of bottom end my xf has a supra turbo (ct26) a front mount intercooler and haltech I get 5psi by 1300rpm but its all over by 3500rpm which suits my needs (towing a car trailer)but sometimes I wish that I fitted a different cam..
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Posted: Wed Jan 12, 2005 9:37 pm 
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Hi guys,

Thanks for the info,

Quote:
Im running a towing cam which gives me lots of bottom end my xf has a supra turbo (ct26) a front mount intercooler and haltech I get 5psi by 1300rpm but its all over by 3500rpm which suits my needs (towing a car trailer)but sometimes I wish that I fitted a different cam..


Is that the max boost your getting (5 psi) ?

Is it all over because of the cam or the turbo size ?

The T3 if roughly the same as the CT26 isn't it ?

Did you put all that on a stock motor and driveline ?


Quote:
.At 050" duration. Its virtually impossible to have zero overlap at advertised duration. Also you want an instense profile, the smallest adv duration possible for the 050" duration you want with as much lift possible. These newer style cams have better idle vaccum and broader rpm range than their dinosaur equivilents.


Is it possible to have a huge lift low duration cam ?

I thought you could only get those in a roller cam ?

Don't suppose anyone does a roller setup for the 250 Crossflow.
Maybe high ratio roller rockers would be the go for high lift ?
But then you cant fit those under the standard rocker cover can you.

Can anyone recomend someone in perth for custom turbo grinds ?

Thanks again

Mike
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Posted: Wed Jan 12, 2005 10:39 pm 
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mikejh wrote:
Is it all over because of the cam or the turbo size ?

Is it possible to have a huge lift low duration cam ?

I thought you could only get those in a roller cam ?

Don't suppose anyone does a roller setup for the 250 Crossflow.
Maybe high ratio roller rockers would be the go for high lift ?
But then you cant fit those under the standard rocker cover can you.

Mike


With that turbo it will be more of the limiting factor than the cam.

It is possible to have high lift small duration flat tappet cams. Most of the profiles are mechanical though C.O.M.E do some good profiles. You don't need a big cam for a street car, 210@050" inlet would be heaps and should easily support 500fwhp with the right turbo. You basically want it to help the motor breathe slightly better, improve low speed torque and help turbo spool. I believe the X-Flow rockers are already 1.73:1 and a roller cam setup would be a waste of money.

I myself am looking to get a single pattern cam with ~200-204@050", 114LSA, and with a 110I/C. This is for a Ford 4.0 OHC, I believe the intake ports are in reality too large and the cam will compensate this. I am aiming for 300rwhp@10-12psi.
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Posted: Thu Jan 13, 2005 10:29 pm 
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Bert wrote:
EBXR8380 wrote:
With little or NO overlap


.....At 050" duration. Its virtually impossible to have zero overlap at advertised duration. Also you want an instense profile, the smallest adv duration possible for the 050" duration you want with as much lift possible. These newer style cams have better idle vaccum and broader rpm range than their dinosaur equivilents.

Na just keep 114 lob centre or more and you'll be fine...Let the turbo make the power....
@50 220 is close 280 adverized..
Btw
A V.L type T3 is small I'd just get latter efi cam....

 

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Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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Posted: Thu Jan 13, 2005 11:18 pm 
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Thanks guys,

Forgot mention it was already an EFI motor, and I noticed crow do an original replacement cam for these, which is the same as their entry level cam.

Are there issues with cylinders 3 and 4 being directly infront of the throttle body (in the plenum). with turbos?

What sort of gains do you think the VL turbo would give, Im not planning on reving this thing too high.

I worked out that the CFM of the 250 at 4500 - 5000 is about the same as the VL at 6500 - 7000.

Does anyone know what the ACL Duralite pistons are like and would they be OK, or should I go for Race series ?

Thanks

Mike
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Posted: Fri Jan 14, 2005 11:16 am 
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Check the compression on the race series...We fitted them to our EDXR6 and had to knock back timing a few degrees to prevent detonation , engine is n/a....
You'll have to talk to ACL and find out what the piston crown is ??This will help http://www.rosspistons.com/calculator.php
CC the heads and go from there...Keep comp around 8.8 or less...

 

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As in ZOOM 126 edition
331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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Posted: Fri Jan 14, 2005 1:09 pm 
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Thanks EBXR8,

I had a look at their (ACL) applications list for the 250 and they actually do an 8cc bowl version which would be good.
The stock comp ratio of the EFI is 8.89:1, so Im guessing these bowl pistons were made for this reason.

It'll be running straight gas most of the time, but its running on my own engine management computer which has dual ignition maps for petrol and gas, also controls gas mixtures closed loop and fuel injection getting added now.

I should be able to prevent detonation on petrol with a conservative igntion map, and the gas should be able to cope with that comp ratio.

On gas Im running 40 degrees at 2000 -3000 atm n/a full load, and 45 on cruise Just a tiny hint of ping around 3 at full load so ill bring it back to 38 or 39.

Mike
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Posted: Sat Jan 15, 2005 10:49 pm 
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At peak torque on turbo engines timing needs to come back quite a few degrees then added safely in upper rpm...You seem to have alot of advance in 3000 rpm ???

 

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As in ZOOM 126 edition
331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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Posted: Sat Jan 15, 2005 11:01 pm 
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Yeah sorry, its naturally aspirated at the moment, Im sure Ill have to take a few degrees out when the turbo goes on, but thats cool cause my timing map can go 1 bar positive.

The LPG loves early high advance due to slow burn speed and actually needs to taper off a bit at high rpms, because its burning almost the same rate as petrol at high rpm.

Mike
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Posted: Mon Jan 17, 2005 1:03 am 
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When you say one bar .Is that above atmosphere or 14.7 ...Generally one bar is atmo at sea level....

 

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As in ZOOM 126 edition
331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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Posted: Mon Jan 17, 2005 1:20 am 
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I designed my computer with a 2.5bar absolute pressure sensor, so it can actually go 1.5 bar above atmospheric, which is about 22 psi boost.

Got it running on petrol today, damn thats some smelly s**t, haven't run petrol for about 5 years now, just straight LPG.
Still got heaps of tuning to do though.

Mike
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