Jump to content

What's the limit?


Recommended Posts

2 hours ago, MichaelH said:

Very impressive and interesting, your engine is 140cc bigger and with the standard crank stroked to 60 thou - I make that 93.5 stroke and +2mm piston size, your engine is 6% bigger and 10% more torque and at higher revs. the other difference is that I run 48DCOEs and you run 45s

Perhaps I should run 45s?

Any thoughts out there

MichaelH

 

 Taken from the Shelsey Walsh thread of about 2 months ago...

 

"On page 2 of 2 Paul (Harvey) kindly lists the engine spec, exhaust, cam etc of his 4a (on 45s) and then swapped the carbs and fitted the 42 Webers and again had a session with Peter Burgess on his rolling road,...and got comparison figures. Unfortunately from 2013 these comparison graphs have been lost however Don H on page 2 of 2 in his comment on these graphs mentions a 5% power and 4% torque benefit from 42s over 45s suggesting a 7 hp advantage (at a guess on a fast road spec engine and a likely 140 ish HP).These give an indication (different day, different weather, different air pressure etc not withstanding) that showed the 42s as giving a much sweeter power delivery with no flat spots over the 45s with same spec engine.

Nice Find Webers - Page 2 - TR4/4A Forum - TR Register Forum (tr-register.co.uk)

Now that was on a fast road spec engine (which many of us would purport to use), rather than a full race spec engine which would likely have a wilder cam and be a right mother to use on the roads, so sightly unfair on the 45s which would deliver better power at revs at least 1000 more than the 42s and certainly be happy at 6k on the clock. Now Kastner used 45s but also used a 5k limit on the engine so I think he would probably have been better running on 42s also. "

...I think the smaller carbs are helping with airflow speed and better mixture especially in the under 5k area, so maybe worth stepping down onto non available 42s ? especially since you'll probably end up at the same size 34 chokes the same size as on your 45s and 48s are likely running at ?

Mick Richards

Edited by Motorsport Mickey
Link to post
Share on other sites
1 hour ago, Motorsport Mickey said:

 

 Taken from the Shelsey Walsh thread of about 2 months ago...

 

"On page 2 of 2 Paul (Harvey) kindly lists the engine spec, exhaust, cam etc of his 4a (on 45s) and then swapped the carbs and fitted the 42 Webers and again had a session with Peter Burgess on his rolling road,...and got comparison figures. Unfortunately from 2013 these comparison graphs have been lost however Don H on page 2 of 2 in his comment on these graphs mentions a 5% power and 4% torque benefit from 42s over 45s suggesting a 7 hp advantage (at a guess on a fast road spec engine and a likely 140 ish HP).These give an indication (different day, different weather, different air pressure etc not withstanding) that showed the 42s as giving a much sweeter power delivery with no flat spots over the 45s with same spec engine.

Nice Find Webers - Page 2 - TR4/4A Forum - TR Register Forum (tr-register.co.uk)

Now that was on a fast road spec engine (which many of us would purport to use), rather than a full race spec engine which would likely have a wilder cam and be a right mother to use on the roads, so sightly unfair on the 45s which would deliver better power at revs at least 1000 more than the 42s and certainly be happy at 6k on the clock. Now Kastner used 45s but also used a 5k limit on the engine so I think he would probably have been better running on 42s also. "

...I think the smaller carbs are helping with airflow speed and better mixture especially in the under 5k area, so maybe worth stepping down onto non available 42s ? especially since you'll probably end up at the same size 34 chokes the same size as on your 45s and 48s are likely running at ?

Mick Richards

When oval racing on a 1600 crossflow Ford, drivers mistakenly believed that an increase in power was consistent with bigger carburettors, ie twin choke twin 45/48 DCOE Webers or Dellortos. 
 

Then Spedeworth introduced the Pinto Ford 2 litre engine for use in this class, and drivers were up in arms and refusing to race unless Spedeworth relented on their ban on the use of twin choke side draught carburettors. Instead the engine specification was for a single twin choke downdraught 32/36 Weber carb. So to prove a point Spedeworth entered a good car/driver with a 2 Litre Pinto engine fitted with twin Weber 45’s into a few races alongside those equipped with the single 32/36 Weber. There was no appreciable difference in straight line speed, and in fact I don’t remember it winning any races.

So surprisingly, the new spec carb proved all those whinging drivers wrong, the engine revved freely and still appeared to deliver power up to 8500, did not ‘bog down’, over choke, flood and misfire coming off the turns like a lot of inappropriately choked and jetted 45/48 equipped cars, and with good, clean low rev traction and torque (provided right cam and advance set). My last 2 litre Pinto engine was built by Toovey of Birmingham, and gave around 168 bhp which I didn’t think was bad.
 

Has anyone yet run a 4 pot TR on the single Weber 32/36 or similar as a comparison, especially for fast road or club use?

http://www.spedeworth.co.uk/rulesdownloads/2020 2.0 Hot Rods as 2020-01-29.pdf

PS and as for steel bottom ends we stopped all that nonsense too. Very expensive and I know of only one Pinto cast crank breaking!
 

Kevin

Edited by boxofbits
Link to post
Share on other sites

Hmmm time for some thought? although the idea that the racing engine is a pain to drive on the road is not found. In my 4A I tried running with the racing cam I had but without the compression 10.5:1 as opposed to 11.7:1 that was a pain to drive. My Present race engine is fine and will trundle at 30mph in o/d top. It will tick over and drive sweetly and only has a little cough at 2.5 K. That has a Compression ratio of 11:1 . The one thing I might do would be to raise the CR to 11.7:1 by skimming the head

Link to post
Share on other sites

175lb ft of torque at 5700rpm is possible with the TR4 engine to the rear wheels, but that's a real race engine (and not a hand grenade), but it's still nothing out of this world BMEP wise. 

I usually figure 100hp / L is a good starting figure for a proper vintage race engine of any type (Spit, BMC A-Series, TR 4-6's, MGB's, etc.). Over that requires A LOT of work, but it's possible. The best A-Series here, are 108hp/L, and still pretty tractable, with SU's and stock valve sizes (rules required in SCCA Production competition). A great Spit engine is going to make 150bhp, or thereabouts. 

Also, keep in mind dyno's vary. Peter Burgess uses a Dynocom which according to the internet, reads a chunk higher than a Dynojet which typically reads higher than a Mustang type. 

Edited by hoffman900
Link to post
Share on other sites

No substitute for driving talent Christian ;) Even Kastner only had 150 at flywheel.

Mick Richards

Edited by Motorsport Mickey
Link to post
Share on other sites

Hoffman's 175 ft Lbs of torque at the back wheels of a 4 cylinder TR4 in a race engine. In that case his race engine must have better flow and more CCs and better fuel and higher compression.

I would appreciate where his engines are significantly better so that I can adopt his methods. Any help is good and I can always learn !

Oh and if I could drive well That would help!

Michael

Link to post
Share on other sites
18 minutes ago, MichaelH said:

Hoffman's 175 ft Lbs of torque at the back wheels of a 4 cylinder TR4 in a race engine. In that case his race engine must have better flow and more CCs and better fuel and higher compression.

I would appreciate where his engines are significantly better 

Michael

Just don't tell Christian how to do it, if he gains the extra 70hp his competitors won't be able to  handle any more angst :lol:

Mick Richards

Link to post
Share on other sites

Driving sure helps, but it's also what your competition has. For example, the vintage B-Sedan classes here (1.8L Datsun 510, 2L Alfa GTV), the front is turning 2:36-2:38's at Road America. Chris, your IMSA TR8 with its previous owner, did a 2:39. A 120hp TR would be lapped by those cars... It's also not going to beat a 150bhp Sprit or a 140hp Spridget, weighing 600lbs less.

175lb-ft isn't a lot for the engine size. I know of 2L engines of similar vintage, but from other country origin, making more than that, and with 2 valves.

There really is no secret. It's an airflow problem. You start with a program like this:http://maxracesoftware.com/PipeMaxPro400.htm

Figure out your power goals and where you want it to peak, it'll help you figure out how much air you need to move, and then work a cylinder head specialists and camshaft designers to get you there. If your guy can't, find someone new, likely you'll have to go outside the little Triumph / BMC cottage industry. Cylinder head specialists vary in their skill, but at minimum, they need to be working on benches that  flow 28" H2O, ideally higher. Again, it's a balance between mass flow and velocity. Lobe designers - don't settle for anything recycled from 1968 and it's going to take over .600" at the valve (and you need to figure out how to make it live), most exhaust systems are lacking, more compression but not at the expense of good combustion, etc. It's all just good race engine building know-how. 

 

Edited by hoffman900
Link to post
Share on other sites

The thing is, many of the 200hp flywheel power claimed cars didn't outperform my weak TR4 on the straight.

conclusion: Maybe the dyno underestimated my car, or the other cars were measured with British air. :huh:

Link to post
Share on other sites
8 minutes ago, hoffman900 said:

Driving sure helps, but it's also what your competition has. For example, the vintage B-Sedan classes here (1.8L Datsun 510, 2L Alfa GTV), the front is turning 2:36-2:38's at Road America. Chris, your IMSA TR8 with its previous owner, did a 2:39. A 120hp TR would be lapped by those cars...

 

Yes, I remember. As excuse, the handling of the TR8 back in 2013 was very unpredictable and Peter and me were always close to the edge of spinning the car from this.

The TR8 gained at Spa over the years about 8 seconds.....it should be faster at Road America now.

Link to post
Share on other sites
3 minutes ago, ntc said:

I have always said the true figure is only on a engine dyno and I challenge anybody to show me the same figures on two rolling roads

Agreed, just too many variables. The rolling road just maximises what you've got...whatever it is.

Mick Richards

Link to post
Share on other sites
2 hours ago, ntc said:

I have always said the true figure is only on a engine dyno and I challenge anybody to show me the same figures on two rolling roads

Engine dynos are just as variable. Sweep rate alone on a water brake will change things. 

 

Chris,

I doubt they do. It's not hard to figure out who's blustering. I think a lot of TR's end up around 180-185bhp. Most are also using the same tried and trued formula. Trap speeds usually show who has what. 

Edited by hoffman900
Link to post
Share on other sites

It would be interesting to get the Hoffman treatment to a 2187cc FIA valve engine running on shell Vmax (99 octane)

oh and by the way what would it cost (apart from import duties)?

I suspect the cost would be the same for FIA as an all out racing engine as most of the cost would be the work done on head and block

Michael

Link to post
Share on other sites
On 10/31/2021 at 7:39 AM, MichaelH said:

Hoffman's 175 ft Lbs of torque at the back wheels of a 4 cylinder TR4 in a race engine. In that case his race engine must have better flow and more CCs and better fuel and higher compression.

I would appreciate where his engines are significantly better so that I can adopt his methods. Any help is good and I can always learn !

Oh and if I could drive well That would help!

Michael

I don’t build engines and am busy with another project. 
 

It would likely be the same or more expensive. More expensive because you are stuck with stock rocker arms, so you’re going to have to go with proprietary lobe designs and cam core to get the lift you need, vs being able to likely use an off the shelf lobe design (say from an older NASCAR application). 
 

Everything else is all going to be custom anyway. Less compression isn’t always a bad thing. Anything with more than a flat top is a compromise in terms of combustion efficiency… does the increase compression offset compression efficiency losses? Especially when you start adding in valve reliefs, etc. It’s a slippery slope. 
 

The best A-Series cylinder head porter here is getting 130cfm sq-in through the throat at 28” H2O on the bench. A TR3-4 head would be around 215cfm using that figure, and no reason it shouldn’t with the right development / person doing it. That value alone will support over 100hp/L with everything else being developed to the same extent. 

Edited by hoffman900
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.