Porting, polishing and BHP
Discussion
Recently I viewed some clips on YouTube showing different guys porting & polishing, with some colourfull comments underneath. One was this clip, and two chaps argueing over its merits. Clicky
Having not started on the engine part of my Cerb resto, I want to get some solid, if not facts, then info about porting & polishing the AJP heads.
My feeling, after speaking to various people in the trade, is that you should polish the exhaust outlets, but not the inlets. And porting should only be done by professionals. Otherwise the flow rates will suffer.
Is this right, a fact, or just opinion?
I'm interested in opinions from all the PH massive, but more importantly from people who have alot of knowledge (Trackcar, Steve Heath, Ridds, et all).
Having not started on the engine part of my Cerb resto, I want to get some solid, if not facts, then info about porting & polishing the AJP heads.
My feeling, after speaking to various people in the trade, is that you should polish the exhaust outlets, but not the inlets. And porting should only be done by professionals. Otherwise the flow rates will suffer.
Is this right, a fact, or just opinion?
I'm interested in opinions from all the PH massive, but more importantly from people who have alot of knowledge (Trackcar, Steve Heath, Ridds, et all).
test port job I've ever seen.
caduceus said:
I'm interested in opinions from all the PH massive, but more importantly from people who have alot of knowledge (Trackcar, Steve Heath, Ridds, et all).
Speaking as a pundit as opposed to someone with actual experience, I would say that in my chav days, porting the head(s) of mainstream cars used to give huge improvements, as they were designed for torque and so were designed to flow the intake mixture faster at the expense of peak throughput.But seeing as the/my AJP produces max torque at 5k rpm, I'm led to believe it was designed for flow instead. Therefore, porting won't have as pronounced an effect as with older cars. But, notwithstanding the fuel atomisation issue, more flow means more potential power, so anything that improves that should help the top end, if that's your bag. I see the exhaust headers as a prime candidate but with the limited space I can't see how to avoid the immediate 90 bend.
I've been privvy to some pretty intesting data both from an engine dyno and a flow bench with many different itterations of a port design with different peoples takes on what's good and what's not. What that guy has just done there is not going to help him much. 
Sometimes, taking material out isn't a good thing. It's all about getting the right shape for the port angle within the head, intake runner shape and area, gas velocity, shrouding in the combustion chamber, how much wall thickness you have in the head casting (that's a funny one when it blows when the engine's running, not) flow seperation, to name but a few considerations.
Personnally I don't think the RR spec actually gives much. It's mostly down to the upped compression ratio and ignition advance.
As for the comments on the vid about using a drill, electic drive can be good (providing you by the right kit) as an air tool gets fecking cold when your porting for a long time!
Sometimes, taking material out isn't a good thing. It's all about getting the right shape for the port angle within the head, intake runner shape and area, gas velocity, shrouding in the combustion chamber, how much wall thickness you have in the head casting (that's a funny one when it blows when the engine's running, not) flow seperation, to name but a few considerations.
Personnally I don't think the RR spec actually gives much. It's mostly down to the upped compression ratio and ignition advance.
As for the comments on the vid about using a drill, electic drive can be good (providing you by the right kit) as an air tool gets fecking cold when your porting for a long time!
Your right about the upped compression, but porting and polishing does work, for example knife edging the throttle spindle is worth a horsepower or two. intake side you don't want to go super smooth as this will not promote tumble. It seems pulse tuning has a part to play, I am thinking of wrapping the air boxes in some insulating material, they must warm up under there.
Back to porting and such , done properly yes it can work.
Though mostly I would guess a standard car would have loads of casting flash ect, it would cost too much to hand finish each car in such detail, and not everyone goes looking for everything they can get.
I've seen the exhaust ports on mine whilst the engine was out, looks like they have been port matched to me, also waisted valve stems, this is all about flow, increase flow increase power.
Back to porting and such , done properly yes it can work.
Though mostly I would guess a standard car would have loads of casting flash ect, it would cost too much to hand finish each car in such detail, and not everyone goes looking for everything they can get.
I've seen the exhaust ports on mine whilst the engine was out, looks like they have been port matched to me, also waisted valve stems, this is all about flow, increase flow increase power.
Edited by Nickccc on Thursday 3rd July 00:05
Chap I respect very much suggested there wasn't a lot that could be done in terms of head-work to seriously increase the AJP-V8 engines' power. That a 4.5 can make 440bhp is quite spectacular for a mid-capacity V8.
This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
It was suggested to me by a good engine builder that teh AJP8 port was good to start with, and certainly the red rose porting possibly adds 10-15hp tops, but you might as well have it as not. There's a PHer though who has had his AJP8 heads flowed and ported and the gains are supposed to be massive, so I'm very keen to get that car on the dyno to see just how much it makes. I know the PHer in question is going to great lengths to get his engine build as perfect as possible so should be a candidate for most powerful AJP8 when it's finished.
Nickccc said:
I am thinking of wrapping the air boxes in some insulating material, they must warm up under there.
FYI - I did a little experiment with this by covering the bottoms of the boxes with headsheild matting and using an IR thermometer to take temps of the intake trumpets after a 5 minute run.Methodology was a little flawed as I was clearly getting some heat-soak in the time it took me to slow down, pull up, open the bonnet etc etc, but I did overall find a 1-2 degree drop - BUT results were not consistant, and there was a significantly bigger difference between individual trumpets on a bank than any difference the shielding made. No.1 (closest to the scuttle) was consistantly the coolest, and showed almost no difference after shielding. Over three runs (plus an initial control run), the other three were showing an average decrease, but temps varied quite a lot both between runs and between cylinders, so I conclude that the results are statistically insignificant. Experiment FAILED.
(plus, I'm reliably informed by Joo that the AJP isn't terribly temperature sensitive, and a BIG difference would be required to have an impact on power).
HTH
Edited by Nefarious on Thursday 3rd July 08:59
I've had the reflective tape on the bottom of the airboxes for ages, the manifolds are directly under them so must make sense to reflect some heat, check the tuscan challenge cars big metal plates above manifolds to soak up some of the heat.
Jules, can you give me a bell please.
edited for picture, this is the stuff I'm on about, from the embasy racing team pits at Lemans 08,
Jules, can you give me a bell please.
edited for picture, this is the stuff I'm on about, from the embasy racing team pits at Lemans 08,
Edited by Nickccc on Thursday 3rd July 10:36
One of my inlet ports.
You can see casting crap and also a lip on the bottom, thats got to cause flow issues.
Well its all been cleaned up and polished now, not ported though as the engine builder says it will decrease flow rate, with everything else that has/is being done it will be interesting to see what it kicks out on the rollers when I finally get the car back, shouldn't be long now.
Mars said:
Chap I respect very much suggested there wasn't a lot that could be done in terms of head-work to seriously increase the AJP-V8 engines' power. That a 4.5 can make 440bhp is quite spectacular for a mid-capacity V8.
This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
Is there anything that could be done for mid range torque Mars? This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
Steve_T said:
Mars said:
Chap I respect very much suggested there wasn't a lot that could be done in terms of head-work to seriously increase the AJP-V8 engines' power. That a 4.5 can make 440bhp is quite spectacular for a mid-capacity V8.
This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
Is there anything that could be done for mid range torque Mars? This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
Also I;v just been reading roadtests on the new Skyline GT-R, Jag XKR-S and Audi R8. 3 cars that have had huge amounts spent on development, the Jag being the most powerful XKR they have produced.
Figures... Engine, 0-60/0-100, Max
Jag XKR-S: 4.2 V8, 410bhp, 4.6/11.0 secs, 174mph
Audi R8 : 4.2 V8, 414bhp, 4.6/11.0 secs, 187mph
GT-R: 3.8 V6, 473bhp, 4.0/9.1 secs, 193mph.
Our 15 yr old Engine (design) isn't really too bad is it?
Superb response chaps. Thanks.
Comments are a bit split as far as opinion goes. But there really isn't enough data as far as the AJP goes, to determine whether porting/polishing gives noticeable gains or not. Although I am interested in hearing the outcome of the car Trackcar is talking about. Massive gains?
The issue of heat/airboxes is something I have been thinking about too, along with certain other issues. As someone already said, to have each car hand finished would be too expensive. So maybe there are alot of small areas that can be improved to make a noticeable difference.
I'm not interested in top end power tbh. More low end and mid range torque would be nice though. Along with smoother running in part throttle situations. Although I know remaps virtually cure that.
I think I'm just after making the AJP the very best it can be, within a budget, along with the rest of the car. Or as close to the condition it was when it rolled out of Blackpool.
Since taking the car apart, I feel I have got to know it alot more, and feel I want to do even more to improve it. Its something that just snowballed, and I just love the car more now than I have ever done, and can't wait till its all back together and ready to fire up.
Thanks again for the feedback.
Comments are a bit split as far as opinion goes. But there really isn't enough data as far as the AJP goes, to determine whether porting/polishing gives noticeable gains or not. Although I am interested in hearing the outcome of the car Trackcar is talking about. Massive gains?
The issue of heat/airboxes is something I have been thinking about too, along with certain other issues. As someone already said, to have each car hand finished would be too expensive. So maybe there are alot of small areas that can be improved to make a noticeable difference.
I'm not interested in top end power tbh. More low end and mid range torque would be nice though. Along with smoother running in part throttle situations. Although I know remaps virtually cure that.
I think I'm just after making the AJP the very best it can be, within a budget, along with the rest of the car. Or as close to the condition it was when it rolled out of Blackpool.
Since taking the car apart, I feel I have got to know it alot more, and feel I want to do even more to improve it. Its something that just snowballed, and I just love the car more now than I have ever done, and can't wait till its all back together and ready to fire up.
Thanks again for the feedback.
yep the AJP8 is a fine engine,
here's some figures from last nights runs for comparrison,
these are with a good spot of wheelspin in first.
Best results ---------------
Time 20:46 Date 30/06/2008
Speed(mph) Time(s)
0-60 04.4
0-100 08.6
30-50 01.3
50-70 01.8
0-100-0 ----
If you want any particular figure 70 to 50 for example just ask and I'll scan the run.
PS cojack, I'll post a picture of my inlet port so you can see the difference, it's pretty obvious.
here's some figures from last nights runs for comparrison,
these are with a good spot of wheelspin in first.
Best results ---------------
Time 20:46 Date 30/06/2008
Speed(mph) Time(s)
0-60 04.4
0-100 08.6
30-50 01.3
50-70 01.8
0-100-0 ----
If you want any particular figure 70 to 50 for example just ask and I'll scan the run.
PS cojack, I'll post a picture of my inlet port so you can see the difference, it's pretty obvious.
JensenA said:
Steve_T said:
Mars said:
Chap I respect very much suggested there wasn't a lot that could be done in terms of head-work to seriously increase the AJP-V8 engines' power. That a 4.5 can make 440bhp is quite spectacular for a mid-capacity V8.
This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
Is there anything that could be done for mid range torque Mars? This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
Also I;v just been reading roadtests on the new Skyline GT-R, Jag XKR-S and Audi R8. 3 cars that have had huge amounts spent on development, the Jag being the most powerful XKR they have produced.
Figures... Engine, 0-60/0-100, Max
Jag XKR-S: 4.2 V8, 410bhp, 4.6/11.0 secs, 174mph
Audi R8 : 4.2 V8, 414bhp, 4.6/11.0 secs, 187mph
GT-R: 3.8 V6, 473bhp, 4.0/9.1 secs, 193mph.
Our 15 yr old Engine (design) isn't really too bad is it?
Nickccc said:
yep the AJP8 is a fine engine,
here's some figures from last nights runs for comparrison,
these are with a good spot of wheelspin in first.
Best results ---------------
Time 20:46 Date 30/06/2008
Speed(mph) Time(s)
0-60 04.4
0-100 08.6
30-50 01.3
50-70 01.8
0-100-0 ----
If you want any particular figure 70 to 50 for example just ask and I'll scan the run.
PS cojack, I'll post a picture of my inlet port so you can see the difference, it's pretty obvious.
I like the less than 2 seconds for 20mph increments myself, now that is serious acceleration here's some figures from last nights runs for comparrison,
these are with a good spot of wheelspin in first.
Best results ---------------
Time 20:46 Date 30/06/2008
Speed(mph) Time(s)
0-60 04.4
0-100 08.6
30-50 01.3
50-70 01.8
0-100-0 ----
If you want any particular figure 70 to 50 for example just ask and I'll scan the run.
PS cojack, I'll post a picture of my inlet port so you can see the difference, it's pretty obvious.
Steve_T said:
Mars said:
Chap I respect very much suggested there wasn't a lot that could be done in terms of head-work to seriously increase the AJP-V8 engines' power. That a 4.5 can make 440bhp is quite spectacular for a mid-capacity V8.
This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
Is there anything that could be done for mid range torque Mars? This is the guy responsible for some of the most powerful K-series engines in Caterhams (one up to 280+bhp).
The ultimate limitation is that it is only a 2-valve design. You can only such so much air through them.
As the AJP stands with the long inlets (like the fingers of each hand interlocked) you are bringing the peak torque down the rev range, ultimately leading to a lower bhp figure and an engine which is all done and dusted at 4500-5000rpm.
Go for a whirlwind induction and you will experience no more peak torque but you will push that peak further up the rev range, and achieve more bhp. Trust me, this is what makes the Cerbera such a brilliant car. Not a huge torque figure for a measly 500rpm in the middle of the overall torque curve. That's the preserve of the RV8-powered Griffs and Chimps. They're like diesels compared to the Cerb... all out of puff just as you get going.
The Cerb is a proper pornographic hardcore racer, and has an engine which can rev to a shade under 8000rpm reliably. Make the most of it. Use it. Revel in it.
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