new punter to the forum

[cheaterparts]

I run a 1979 sigma Improved Production circuit car atm still running a 4g54 NA it has dynoed to 119.5 Kw atw and I have a few more bits made to pick up a bit more power but I think the 2.6 will top out around 130 Kw atw

so its time to look at a turbo and to stay in the same class ( 2001 - 3000 )the engine needs to stay under 1764 cc as there is a 1.7 multiplying factor
1764 x 1.7 = 2998
so the game plan is to use a 4g61t as a base
bore it to 85 mm and use *63 forged 9:1 pistons making 1702 cc
that will be using 147 mm H beem rods
that should give a comp ratio with the short stroke of about 8.3 : 1
I have a large port *67 head that will get some port tickling and some stainless valves
I will use a GT2860 and need to fab up a tube header to suit
the engine choice will work out quite good as the engine will bolt up to the gear box my light flywheel and tilton race clutch will also fit up
i will need to make up a new sump and some engine mounts

anyway that the plan hopefully I'll have the turbo engine ready for late in the year
till then the old 2.6 will keep me running

I see that a few on the site get around a fun/sprint days and hillclimb
I may catch up with some of you as I do get let out to play every now and then

hopefully my next play day is in 10 weeks at sandown thats the next state race round

 

[OFFON-4]

Sounds like a track demon!!!

Post some pics up and welcome 8)

 

[GSR94T]

welcome dude

love the old sigmas

my first car when i was 17 was a 1979 Chrysler Sigma (of course same as mitsi as all would know)

but it had the astron 2L lol ... i miss that car

funnily enough the guy that bought it off me said he wanted it for parts for a rally car, but instead turned it into a rally car and left the original registration plates on it.

http://www.amsag.com.au/amsag.net/images/gallery/hampton2006/pages/_4018543.htm

 

[GSRSOL]

sounds great ! welcome

 

[CLuTZ]

120kw atw from an N/A is damn impressive- I can imagine it being a light car too!

As for the choice of motor, the 4G61 is a very sturdy little engine, much like its big brother the 4G63.

I was going to say, using the 4G67 head will be the way to go, but you seem to be already down the right path!

Are you sure you can get 85mm out of the 4G61's bores though?

 

[cheaterparts]

my first car when i was 17 was a 1979 Chrysler Sigma (of course same as mitsi as all would know)

but it had the astron 2L lol ... i miss that car

strangely enough I remember when they came out as a new car I had been on the road for a few years and a mate bought one new ( I'm showing my age )
although they are a bit old school now at the time were quite a flash car

I bought mine about 1995 and drove it for a couple of years the poor old 1850 was getting a bit sad and I picked up a GH cheap
In 1999 a couple of mates slimed me into hillclimb so the GE was caged a couple of webers fitted. the car was log booked ( cams ) at that stage ran a 2Lt and the best figures N/A were 84 Kw atw after a bit of playing with the engine
I'm sure more power would have been found with the 2Lt however a 2.6 was fitted with a lot more cam a ported magna head and some other work
and that has been an ongoing project
with the car in 2.6 trim I won the 2004 Aust hillclimb champ for 2001-3000 improved production
for the guys that have played at morwell the time was 35.87 sec

120kw atw from an N/A is damn impressive- I can imagine it being a light car too!

Are you sure you can get 85mm out of the 4G61's bores though?

the car last time it was on the scales was 990 Kg
120 kw and that is at 6100 athough the engine easy spins past 7000
in fact to save a gear change at sandown . it spins to 7200 in 4th on the front straight

as for the bores on the *61 I'll do an ultra sound on the block first to see how much material there is
but the is a b plan if there isn't enough I'll slide the short stroke crank into a *63 block and the deck will need to be machined about 4 mm and there looks to be enough material to do this

 

[CLuTZ]

I guess thats another thing- the 4G63 is already 85mm- have you thought about de-stroking using a 4G61 crank? Should allow you to rev alot higher!

 

[cheaterparts]

I guess thats another thing- the 4G63 is already 85mm- have you thought about de-stroking using a 4G61 crank? Should allow you to rev alot higher!

the biggest problem with IPRA rules on turbos is that a 36 mm restrictor neads to be fitted to the inlet side of the turbo 50 mm from the wheel
this cuts flow so also cuts the reves
about 7000 revs will be max as the flow here is about it
the boost will be droping to maybe 15 pound and like wise the inlet temp goes up a lot as the turbo is trying to make boost with bad inlet flow

but this will be ok the larger engines suffer more
I know of a 2.3 twin cam under our rules had to change at 5800 as that was it
one of the very quick cars from SA an 808 mazda with a bp18 runs no waste gate his max boost is at 5500 22-26 pdsi and is back to 16 at 6500

still the turbo guys are getting 180 -190 kw atw which is 50 -60 more than I have as N/A and the weight will be about the same maybe a little down on what I have
about the only place I can see the turbo being slower is off the line where the 2.6 will grunt under the cam and the turbo will need to spool
but with 8 laps and only one start that can be lived with

 

[EVO-00X]

Welcome Sounds like you've got it sorted and thought about things beforehand. Good to see you're going the oversize stainless valves to improve flow and also just as important by keeping the valvetrain cooler . Choosing the right size midrange turbo and boost levels will give you an awesome little engine. Just wondering whether a small increase in CR would work out a bit better for you, depending on the amount of boost pressure you want to run out of it of course, and how long you can maintain it without the restrictor posing an issue. i.e. no point running as high a boost level if the extra boost is going to be restricted, therefore compensate by lowering boost levels and improving off boost response by raising CR If you are only going to run 15psi, then I'd be upping the CR more

 

[cheaterparts]

Welcome Sounds like you've got it sorted and thought about things beforehand.
Good to see you're going the oversize stainless valves to improve flow and also just as important by keeping the valvetrain cooler .
Choosing the right size midrange turbo and boost levels will give you an awesome little engine.
Just wondering whether a small increase in CR would work out a bit better for you, depending on the amount of boost pressure you want to run out of it

I've been building engines for a while and always the best way to start in to plan the mods in advance it save a lot of money
bronze guides will go in as well again that tranfers heat better and stops a lot of scuffing
the choice of turbo had me thinking and I was looking at ether the gt2860 or gt2871 both looked to have the flow chart in the ball park
but I'm going to run with a gt2860 with the small ex housing these spool fairly quick and the ball bearing turbos last better with a restrictor
as for the higher comp I agree my rough sums using .63 9:1 pistons comes out at 8.3:1 and I would like to run more , but untill all the engine bits are side by side and some measuring is done I wont know the final comp ratio

 

[CLuTZ]

Just wondering whether a small increase in CR would work out a bit better for you, depending on the amount of boost pressure you want to run out of it

as for the higher comp I agree my rough sums using .63 9:1 pistons comes out at 8.3:1 and I would like to run more , but untill all the engine bits are side by side and some measuring is done I wont know the final comp ratio

I agree also! What you can make up for in displacement to spool the turbo, you can make up for with CR, especially if you have to use those restrictors (that would give me the shits) :lol:

 

[cheaterparts]

especially if you have to use those restrictors (that would give me the shits) :lol:

its a sore point those with turbos want ether a bigger hole to suck through or no restrictor at all and those that run N/A think the the hole should be smaller

but the balance is good last w/e phillip island a destroked ca18 turbo came had a 1st place 3rd and dnfed the last race but still ran a 1:50
thats outright
the banger V8s run around that time I think a 1:49 was the quickest lap time for the w/e ( 350 chev powered commodore )

the lap record at sandown for IPRA is held by a 808 mazda with a 1800 turbo
with a time of 1:19 these cars have to run the restrictor
the quickest V8s run 1:20s

of cause the best part about play the turbo game is the cost factor
a mate is building his V8 chev in a VL which will be a quick car
the engine will owe him $30,000+ now to do the baby twin cam turbo including turbo will be under $5,000 and should run around the same times
I prefur my budget