43 replies to this topic

[IronmanG]

I was under the impression that 8 ports were supposed to produce better torque than the 5 port.

I think the 8 ports are ok as the ports are small. The 7 ports are to big so air speed is too slow so its not until 5000rpm that the torque is level with a 5 port.
Pound for pound the 5 port has more torque until the higher rev range

I think its such a shame about the current 7 port head as the idea is an excellent way round producing great power, I believe the heads are cast in the USA by a company called Pierce? why the company that flogs them over here doesn't ask for the ports to be cast smaller seems a bit wierd, with the right size ports you would think a +10FTLB per litre would be on the cards. An enterprising type of guy could take a bare casting to the Chinese tell the to copy it but with port revisions, then harden it properly and be on a right winner, especially if you got a common plenum designed and cast up at the same time, as this would bring the supercharged crowd into play as well.

Shooter

They use to use 40mm itb with them that went down to 38mm which is still to big. Not sure what the port size is on the 8 ports. More like 32 or something?

Edited by IronmanG, 08 July 2023 - 02:32 PM.

[Ethel]

Interesting article, Spider,

 

I'd assumed the cam was sited in conjunction with the head stud pattern so the rocker posts would collocate & allow the ports to pair up for space & cost efficient manifolding. 

 

It would almost design itself, applying the principle of minimum parts in the least space - with pushrods & rockers

[Shooter63]

I was under the impression that 8 ports were supposed to produce better torque than the 5 port.

I think the 8 ports are ok as the ports are small. The 7 ports are to big so air speed is too slow so its not until 5000rpm that the torque is level with a 5 port.
Pound for pound the 5 port has more torque until the higher rev range

I think its such a shame about the current 7 port head as the idea is an excellent way round producing great power, I believe the heads are cast in the USA by a company called Pierce? why the company that flogs them over here doesn't ask for the ports to be cast smaller seems a bit wierd, with the right size ports you would think a +10FTLB per litre would be on the cards. An enterprising type of guy could take a bare casting to the Chinese tell the to copy it but with port revisions, then harden it properly and be on a right winner, especially if you got a common plenum designed and cast up at the same time, as this would bring the supercharged crowd into play as well.

Shooter

They use to use 40mm itb with them that went down to 38mm which is still to big. Not sure what the port size is on the 8 ports. More like 32 or something?

Would it be worth filling the bottom of the ports with Devcon on the 7 porter to raise the port velocity?

Shooter

[IronmanG]

I'm currently making an airbox to try and increase air speed

[sonscar]

I would be interested in your thoughts on that.I have a bigger brother 1860 B series MGB which I injected almost 20 years ago.After many experiments I made a plenum with single throttle body and the driveability was massively improved.A larger body killed the driveability so was removed.This was all done with scrap parts.Steve..

[IronmanG]

I've talked to AC about it and some other knowledgeable guys. The rolling road road guy was massively underwhelmed by it and just said why don't SC just sell an airbox and single throttle body for improved performance and much cheaper cost. AC said try putting a n airbox with as long a pipe as you can fit.
I'll put a couple of pictures of what I'm doing. I've adapted my existing filter by taking the foam off it and laying carbon fibre over the top. Then running a 50mm pipe behind the grille to a KN universal filter.
I've done it so that it can be changed quickly using the existing backplate, so its only a test and nothing else is changed so I can put it back really easily
Its total guesswork really but as a secondary it might get rid of the awful drone between 3200 and 4000 and if I'm lucky pep up the torque without sacrificing top end, because to be fair at 7000 its singing

[IronmanG]

 Screenshot_20230709-085242_Gallery.jpg   18.47K   4 downloads  Screenshot_20230709-085254_Gallery.jpg   18.81K   4 downloads  Screenshot_20230709-085316_Gallery.jpg   10.92K   4 downloads  Screenshot_20230709-085628_Gallery.jpg   13.62K   3 downloads

Its cost maybe hundred quid to do as I don't have many scrap parts but I'm a nerdy experimenter and after spending what I already have.....

[sonscar]

My MGB has trumpets inside and was this size as it was all the ally that I had.Steve..
Ps be aware of the distance from the trumpets to the air box lid as too close kills performance from my trials.Steve..

Attached Files

•  IMG_20230709_102332.jpg   69.55K   1 downloads
•  IMG_20230709_102307.jpg   75.18K   2 downloads

Edited by sonscar, 09 July 2023 - 09:32 AM.

[IronmanG]

Yep aware of that. It was a major sticking point when fitting it all in the car. On the ITG website they state minimum 15mm from trumpet face to inside of filter. If this works I will try and build a little more into it if I can

[IronmanG]

I'm running up the prototype airbox today just to see what happens. Currently at tickover the AFR gauge shows between 13 and 13.2 once warm.
So if the airbox is doing its job and providing faster air flow I can expect to see that number rise slightly?

[sonscar]

Depends on if you have AFR correction fitted and enabled.Steve..

[IronmanG]

Depends on if you have AFR correction fitted and enabled.Steve..

Ye I thought that as I typed it🙈

[Ethel]

If circumference  x height =  x sectional area

 

h x pi x 2 x r =  pi x r x r

 

height = radius divided by 2

 

40mm ram pipe needs 10mm of gap minimum.

[Mite]

Late to the thread. Thinking about the comparisons between the A-Series and Nissan's own developments from the MA, with the exception of the lean-burn and all-alloy aspects (making the Nissan unit some 40-50kg lighter) to what degree could it be said the latter was a pretty close approximation to what was intended with the stillborn (alloy-head?) A-OHC prototype envisaged at one time for the Metro?

There was already a Mini conversion with the MA engine years back before the related CG and CR engines (with A-Series esque 1275-1386cc capacities) became popular swaps even in Spridgets. Arguably being better spiritual A-Series successors by virtue of their trace Austin lineage, than even the K-Series without the infamous reputation associated of the latter. Have to wonder if the Nissan units would perform similarly well swapped in the Metro as they do in the Mini.

As to how the Nissan designs are related to the Austin designs. Basically AFAIK Nissan started out with a licence built 1.5-litre B-Series, reduced it to 1.0-litres for the C engine before enlarging it to 1.2-litres as the E OHV and later becoming the J 4/6-cylinder as it gradually strayed from its B-Series roots.

That linage would be replaced by the all-new Nissan A OHV (despite its name it’s in reality sized between the BMC A & B) that integrated all improvements it made to the Austin rooted designs by that point (yet still retained some trace elements), which in turn would spawn the E OHC whereupon it evolved into the GA and maybe QG (think something analogous to an uncorrupted properly developed small-block BMC E/R/S-Series without the E6), was enlarged to became the CA / CD (think something like the O/M/T-Series & Perkins Prima/L-Series for diesels) as well as scaled down to became the MA / CG / CR.

Even though the SR replaced the CA, have not seen anything to suggest it was anything other than an all-new design and many of the other designs above were eventually replaced by those developed together with Renault.

Edited by Mite, 03 March 2024 - 02:08 PM.