ALWAYS check an unknown engine build.

All Technical Tips an Tricks' will be located HERE merged from all the forums above.

Re: ALWAYS check an unknown engine build.

Postby geezer101 » Thu Jun 23, 2011 2:05 pm

O.K. have to add my two bits. A lot of engine builders do not recommend linishing/polishing stock rods as they're more likely to fail. The theory used to be that a polished rod is "de-stressed" but the removal of material does nothing more than remove material. Only go option 2 if you're prepared to spend big$$$, and that's billet alloy rods. Another thing (but not really relevant) is detailing inlet manifolds. Guys who build hi-po NA engines don't recommend polishing inlet manifolds, it somehow robs the engine of torque. And no, I don't know why...
geezer101
 
Posts: 1864
Joined: Sat Jun 11, 2011 10:49 pm
Location: adelaide (SA)
Country: Australia (au)

Re: ALWAYS check an unknown engine build.

Postby cheaterparts » Thu Jun 23, 2011 7:33 pm

geezer101 wrote:O.K. have to add my two bits. A lot of engine builders do not recommend linishing/polishing stock rods as they're more likely to fail. The theory used to be that a polished rod is "de-stressed" but the removal of material does nothing more than remove material. Only go option 2 if you're prepared to spend big$$$, and that's billet alloy rods. Another thing (but not really relevant) is detailing inlet manifolds. Guys who build hi-po NA engines don't recommend polishing inlet manifolds, it somehow robs the engine of torque. And no, I don't know why...


I must say I haven't met one engine builder that doesn't recommend preping rods - unless they are being replaced by after market rods

the theory was and still is that by removing stress points on a rod will reduce failure - so polishing the beams does this
however after cleaning up the rod they must be shot peaned to put back a toughened skin on the beam

after market rods are mainly billet or forgings that are fully machined from steels like 4340 and are also shot peaned as the end process for the same purpose

as for aluminium rods they arn't much good for steet use or circuit cars as they have a very limited life span

as for polishing the inlet track ( manifolds and inlet ports ) yes it does rob power from reduced air flow
a polished surface has more drag than a matt finish so flows less air
if possable polish the exhuast ports though it slows down the build up of carbon
cheater
User avatar
cheaterparts
 
Posts: 658
Joined: Tue Mar 17, 2009 9:06 pm
Location: Cranbourne Vic

Re: ALWAYS check an unknown engine build.

Postby astronturbo77 » Thu Jun 23, 2011 8:30 pm

i was taught that polishing inlet ports dosent let the fuel atomise and forms droplets instead of being a mist going into the cylinder.
BUILT NOT BROUGHT BY ALGIE.
astronturbo77
Sigma-Galant Police (Global Mod)
 
Posts: 1356
Joined: Thu Mar 26, 2009 8:09 pm
Location: Hobart Tasmania
Country: Australia (au)

Re: ALWAYS check an unknown engine build.

Postby geezer101 » Thu Jun 23, 2011 10:14 pm

Sorry I did a typo on my last entry- forgot the "/" between the billet and alloy. The polished manifold was actually relating to the external surfaces. It is to do with increased surface area of cast aluminium? Heat sink effect maybe... Saw a guy doing 8 cyl engines saying every time he dyno'd a motor, he got a constant 4-6lb drop in torque if the same motor was fitted with an identical but dressed inlet manifold. Weird.
geezer101
 
Posts: 1864
Joined: Sat Jun 11, 2011 10:49 pm
Location: adelaide (SA)
Country: Australia (au)

Re: ALWAYS check an unknown engine build.

Postby Superscan811 » Mon Jul 04, 2011 8:20 pm

Well, I took the car out yesterday with Matt for a quick check on the 40-110. The time was around 12 seconds. Not very happy with that. I was running the engine a bit lean at the time so I decided to fatten up the AFR a bit.

It made a bit of a difference.

This is a 15 second log from the run.
110kph in 3rd gear is 4200rpm (the white vertical line), I checked it via GPS on the way home.
Image
Much better, down to 8.3 seconds, and over 1 second quicker than my best time before the engine rebuild.
:D

Cheers.
Superscan811
 
Posts: 1669
Joined: Sun Mar 22, 2009 4:12 pm
Location: Sydney
Country: Australia (au)

Re: ALWAYS check an unknown engine build.

Postby Rally_2.6LC » Tue Jul 05, 2011 9:42 pm

So do we need to go testing again???? :D


Cheers Matt
'75 GC daily (slowly dying)
'80 LC 2.6L rally car (generally something broken until 2 weeks before an event)
'71 GA 2.6 Turbo project (i only wanted the diff and got another project)
^This side up^


Formely "Matt"
User avatar
Rally_2.6LC
 
Posts: 938
Joined: Sun Mar 22, 2009 10:59 am
Location: Either under a car, on the computer or in bed...around Ryde
Country: Australia (au)

Re: ALWAYS check an unknown engine build.

Postby Superscan811 » Wed Jul 06, 2011 12:32 am

Matt, just for a comparison

The top graph was using 1.48mm main jets (your run) and the bottom graph was using 1.55mm jets (my run).

Image

At 6.90 seconds, on your run, the engine close to 5700rpm whereas I was at 6000rpm.

With a .07mm increase in jet size there was a 0.6 of a second difference to reach 6000rpm (in 2nd gear).

Looking at the AFR on my graph, I could probably go to 1.57mm.

Probably should dial the cam in properly before doing too much more, seeing I just set it by guess.

Hmm.

Cheers.
Superscan811
 
Posts: 1669
Joined: Sun Mar 22, 2009 4:12 pm
Location: Sydney
Country: Australia (au)

Re: ALWAYS check an unknown engine build.

Postby Superscan811 » Sun Aug 07, 2011 12:12 am

After a few minor changes, the latest Dyno run netted nearly 100kw at the wheels..

Image

Hopefully there is still a little bit more but not willing to push it too much further. It was built as a daily, not for big power...

Cheers.
Superscan811
 
Posts: 1669
Joined: Sun Mar 22, 2009 4:12 pm
Location: Sydney
Country: Australia (au)

Previous

Return to Technical Tips an Tricks'

Who is online

Users browsing this forum: No registered users and 1 guest