Fiat Punto HGT - Engine Rebuild

Road-race engines and ancillaries - general discussion
WhizzMan
Posts: 459
Joined: Fri Aug 13, 2010 8:05 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby WhizzMan » Sat Dec 10, 2011 1:36 pm

You still have the hydraulic tappets I believe? If you want substantially more power, you most likely will have to go higher up the rev range. That will require solid tappets, different cam profile, different piston springs, possibly bigger valves and a porting job that is matched to the flow you will be needing to get to that power. Basically, everything in the head will need to be taken to the next level. I don't know if I would want to do that with a 1800 myself. Even if you're not going up the rev range but "only" for bigger valves, you still need a lot of work done.
Book #348

iceman_n
Posts: 21
Joined: Sun Nov 27, 2011 9:18 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby iceman_n » Sat Dec 10, 2011 5:09 pm

Yes I have hydraulic tappets...I am thinking to replace my Colombo camshafts with a set of Cat camshafts...

Specs :

duration [0.1mm+cl] 291° - 278°
duration [1.0mm+cl] 252° - 244°

maximum lift [cl=0] 10.75 - 10.00mm
lift at TDC [cl=0] 3.65 - 3.10mm

timing [1.0mm+cl] 21/51° - 47/17°

REQUIRED PARTS : followers CC002 , retainers O.E.M , springs O.E.M

But without any other modification in cylinder head...

WhizzMan
Posts: 459
Joined: Fri Aug 13, 2010 8:05 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby WhizzMan » Sun Dec 11, 2011 7:31 am

Just getting a single part replaced to gain you a certain HP number is not how tuning engines works. Every boy racer that has bolted on a noisy exhaust, "power filter" and a chip from eBay thinks he's just added 40% to the power of his engine. In reality, very rarely do they get even close to that figure, when the car gets tested on a dyno. More often than not, they are down on power, compared to stock. Changing your cam profiles will require a new flow strategy and most likely, reworking your head and possibly manifolds to match that.

Keep in mind that all the parts in the engine are a combination. if you change one thing, it is very likely that you will have to change others to benefit from the part you changed initially. Sometimes, you have to change parts to even just make the engine run at all. Often, a gain on one end, will cost you dearly at another place. Just going for maximum horse power may make the car hard to drive and slower on the road or track. I would recommend that you will think through carefully what direction you want to go. After that figure out what cam timing, flow rate, compression and all other factors you need for that. Then get all the parts that will get you there and do the machine work to the head and optional other parts.
Book #348

iceman_n
Posts: 21
Joined: Sun Nov 27, 2011 9:18 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby iceman_n » Tue Dec 13, 2011 10:15 am

Mr Croft can you tell me more details about this :
viewtopic.php?f=6&t=1431&p=7580&hilit=punto+hgt#p7580

If you know cam specs, mechanical lifters, valve are Fiat ones or aftermarket, springs and retainers ?
How it is possible to run without shims ? I think that is possible to damage the valve...

Guy Croft
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Re: Fiat Punto HGT - Engine Rebuild

Postby Guy Croft » Tue Dec 13, 2011 10:23 am

"Changing your cam profiles will require a new flow strategy and most likely, reworking your head and possibly manifolds to match that"

Not true, not as a general rule anyway. A change of cams can yield good results (not always, depends how good the cam desing is compared with the OE setup, header, CR..) but be in no doubt that unless the engine management system is remodelled to tell the engine about the new inlet and exhaust event there will likely be power loss and sever risk of detonation.

But if the cam supplier cannot substantiate power gains (from actual test) with the new cams you don't know what you're buying.

GC

WhizzMan
Posts: 459
Joined: Fri Aug 13, 2010 8:05 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby WhizzMan » Thu Dec 22, 2011 9:33 am

My apologies for wording it so strong without any example. What I meant to bring across is that if you make drastic changes to your cam profile because you want a lot more power from your engine, you should have a head that matches the flow requirements from the cam.

Imagine your original engine is designed to give good torque between 2500 and 6500 rpm, peak power, 135 BHP around 6000 rpm. If you want that engine to give 190 BHP, you will have to make it go at least 7500 RPM, probably over 8000 and the usable torque will not be available under 4500 rpm. To get all that extra fuel required for the extra power burnt, you will need to be able to flow a lot more air through your ports. Putting a "fast" cam in a head that is optimized for the 135BHP example, will not make the head pump much more air, because the ports are too small. Going for an engine that will run 7500 RPM and above for substantial amounts of the time, will require a change to solid tappets. The weight and design of the hydraulic tappets will no longer be sustainable at that RPM rate.

From what I understand, you have a "fast road" setup now, that still gives considerable attention to low RPM drivability. My interpretation is that you want to get substantially more power out of your engine and the only way I know of doing that, without using a turbo or compressor, is going for the full race high RPM configuration. That is a totally different way of setting up an engine, hence my post about having to do a lot of work. I hope this makes my previous post more clear.
Book #348

iceman_n
Posts: 21
Joined: Sun Nov 27, 2011 9:18 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby iceman_n » Sun Dec 25, 2011 10:01 am

New rods finally ready...
440grams instead of 688grams Fiat ones...
H beam shape
This is my Christmas present :)

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iceman_n
Posts: 21
Joined: Sun Nov 27, 2011 9:18 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby iceman_n » Fri Jan 06, 2012 6:26 pm

Finally ready...

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iceman_n
Posts: 21
Joined: Sun Nov 27, 2011 9:18 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby iceman_n » Fri Jan 20, 2012 4:25 pm

Engine works fine, I have done around 200 miles
I will change oils and i will make an other 1000miles...at the end of the month i will go to my mapper to connect the idle valve and make some changes to fuel/ignition maps...

fingers99
Posts: 99
Joined: Wed Dec 09, 2009 6:24 pm

Re: Fiat Punto HGT - Engine Rebuild

Postby fingers99 » Sat Jan 21, 2012 10:34 pm

Almost certainly some combination of the above.

All the talk is that these engines are less amenable to tuning than the old FIAT twin cam and the 20v Coupe engine (which a few people have put into HGTs).

I think the final set of BTC Alfa 155s used the 2 litre version of the Alfa/FIAT twin cam -- the precursor of your engine. It would be interesting to know how much power they were putting out -- they were fast enough to be the car to beat.
GC_06


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