Broken Alfa Nord Race Engines

Competition engines and ancillaries - general discussion
timinator
Posts: 116
Joined: March 9th, 2011, 5:20 pm

Re: Broken Alfa Nord Race Engines

Post by timinator »

WhizzMan thank you for clarifying what Richard was saying. Although I have not had the experience of installing a cam with 20 deg. less duration and maintaining the same absolute top horsepower figure. I suppose it is possible.

I have had the situation where the cylinder wall of a Ford 7.5 liter with 13.5cr cracked. We solved the cracking problem on the next block by filling the top 1 inch [25.4mm] of the water jacket below the deck with an epoxy substance. I am not suggesting that Richard do that however.

I would suggest that Richard look up a dynamic compression ratio calculator online to determine what his actual ratio is for the cam he has instead of using his staic compression ratio to base his assumptions on.

Finally, because of the cost of replacing broken engine parts, it would be worth while for Richard to invest in some diagnostic tools. These tools could include an exhaust temp. gauge, intake air temp. gauge, and wide band O2 sensor. I would also suggest a knock sensor with the stipulation that it be used for data gathering rather than engine protection.

Please excuse me if I seem off putting in my posts, because typing is difficult for me. I try to use the least possible number of words.

Tim
WhizzMan
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Joined: August 13th, 2010, 8:05 pm
Location: Amsterdam, the Netherlands

Re: Broken Alfa Nord Race Engines

Post by WhizzMan »

It's just an assumption on my part, it may be he means something different. I agree that using diagnostic equipment during adjustment and open trainings, would help find out what is actually happening inside the engine. What is posted in this thread suggests it has most likely to do with engine knock. Putting on a knock sensor and a wideband O2 sensor would at least confirm any knocking condition and the fuel mixture.

With the cam angles at 320/300, high static compression is not that strange and will usually not lead to too high dynamic compression. However, if you're not allowed to run over 95RON or maybe 98, it still may be too high. I know there is a relatively large group of Nord racers in the Netherlands. Maybe they can reveal some of their secrets?
Book #348
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Sorry to be slow in coming back to this - lot on my plate right now only part of which has been a 1000-mile round trip to collect my race car.

First, the good news: car ran on the rollers and delivered an estimated 190bhp with a reasonably broad power band - pretty much even from 6000-7000rpm. This was done on an "old-school" set-up so please don't ask for print-out of anything (Pete Baldwin for anyone that knows). Even determining power is by experience and comparison - but safe to say it was putting out close to 40bhp more than a well-built 1500 Sud race engine.

Went up a size in venturis - 38mm. Optimum max advance was 33deg. Proof of the pudding will be on the track this weekend - 80 laps over the day to see what it will do - I've driven Knockhill so much that it will be readily apparent if there's more power on tap.

As for the other discussion above - I'll post a picture of the detonated piston as soon as I can - that'll give a clear indication of the dome. And, yes, it was an increase in peak torque (don't remember at what rpm though the graph above may help) without much influence on peak power(7200 rpm).

As per my post above, I'm planning on building another engine as I get to understand more of this. There's not a huge amount more power to be had from a Nord - but I would like to optimise it. One day (budget allowing) I want to have a GTAm engine built but, before I go to that expense, I'd really like to have a much better handle on things.
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

timinator wrote:

Horsepower is calculated by a formula using the engine torque output. If you have higher torque it follows that horsepower must increase. 'No significant loss in power' is not a possibility. As you have already witnessed it is easy to install a cam that does not work well in your engine when you have no experience to base that selection on.

Tim
Thanks, Tim. Just to be a bit more specific on this. That shorter duration of the exhaust cam was at the behest of the original cam designer. He'd done both simulations and then engine dyno testing of these cams to validate the design. So it wasn't just a guess on my part.

That the engine seems to be delivering pretty good and broad power and the RR operator/tuner was suitably impressed by the pick up throttle response of the engine suggests that the cam designer probably wasn't too far wrong.

With the help of Guy and a bit of bitter (but useful) experience, I'm beginning to piece together the elements of what works and, more importantly, why it works.
timinator
Posts: 116
Joined: March 9th, 2011, 5:20 pm

Re: Broken Alfa Nord Race Engines

Post by timinator »

Richard, sounds like loads of good news for you. Just as a note on dyno tuning, it is possible to run more timing on the dyno than you can run safely on the track. Might ask your tuner what he thinks about adjustments based on conditions on the track.

You also experienced something I have not encountered with engine timing. I usually creep up on timing with new to me engine setups starting at 30deg. total timing. The power usually starts to drop like a rock after peak output is achieved. Going 9deg. above peak timing seems amazing that you could maintain 170 hp.

GC's discussion on detonation was of course spot on. I would like to add one small addition though. It is called charge stratification. Basically gasoline is made of components that have different weights. The lighter weight components burn easier than the heavy. When they separate in the combustion camber due to heat and pressure- stratification- is when things go bad. I would suggest obtaining a portable weather station so that jet changes could be made at the track. Could be why you are cracking liners during the racing season. Good luck.

Tim
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Thanks again, Tim.

I'm reasonably sure that the timing is optimised. The operator's method of checking the optimum max advance is to literally manually swing the dizzie whilst observing the power output on the dyno. There were a number of differences between this set-up to the engine tested previously. These included (at least) the inlet valves, the venturis and the jets. I don't have enough experience to say if these changes would allow for this change. For sure at the previous timing we were getting significant det.

I do have a record of temp and ambient pressure at the rolling road. The RR operator also indicated that I should go down a size of jet if I race in warmer conditions. That said, I race at Knockhill in Scotland - I've raced there on days when it's snowed and low temperatures and drizzle are the norm. I have a mobile weather station so I can add that to my racing kit.

He also said to take care on the age of the fuel I've used - keeping it as fresh as possible and from a filling station with high turnover. We also had a discussion about octane improvers. I had a conversation a while back with someone from Elf Fuels competition department who said that they were totally useless.

I know Guy is passionate about this final point but I finally witnessed it for myself - full-radius trumpets add power. The Sud owner had traditional and full-radius trumpets of comparible length. The full-radius pipes added 4bhp to peak power (delivered at a slightly higher rpm). That's a very cheap 4bhp.
rmerrell
Posts: 33
Joined: July 8th, 2011, 11:13 am

Re: Broken Alfa Nord Race Engines

Post by rmerrell »

Guy - would you gap the B9EGV plugs the same as standard plugs (25thou) and can I get away with a larger gap with an electronic ignition system? (30+)?

I've been looking into airboxes and probably the simplest would be to source a GTA replica airbox in GRP as it should fit. GRP seems to have the benefit of being a reasonable insulator so shouldn't conduct heat into the airflow. Good idea?
Guy Croft
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Re: Broken Alfa Nord Race Engines

Post by Guy Croft »

They come pre-gapped at 23thou and I've never altered them. I don't think it matters overmuch whether you use 23/25/30thou more depends on the power of your ignition system.


G
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