Big cams, OE manifold, way down on power.
Discussion
Inline__engine said:
if you want an engine sim then use ENGMOD4T and the new version of pipemax.
this engine looks like it was designed based on 2V/cyl push rod engines meant for drag racing.....
if you tell us
bore
stroke
rod length
Bore, stroke and rod length are basically irrelevant. The differences they make are tiny.this engine looks like it was designed based on 2V/cyl push rod engines meant for drag racing.....
if you tell us
bore
stroke
rod length
DeadCatWalking said:
227bhp said:
So you think the ex cam is actually losing power?
Which bit of "Much of the combustion power is going straight down the exhaust pipe" was unclear?My best guess is that exhaust cam is costing 10-20 bhp.
227bhp said:
The exhaust is debatable and others would disagree. As I see it it's not costing me power, it was done so it couldn't be suspected of holding the engine back.
How dare you disagree with me or quote pretenders to my throne who do! I am a tuning god. Overly large exhausts (both manifolds and systems) almost always cost power and more importantly torque. Read the articles again.Manifolds are more important than systems but both can hurt if oversized.
I've read your articles before, the exhaust one states " this article considers the ideal diameter of exhaust system to be non restrictive for a given power output."
It makes no mention at all that going too big will hurt power, maybe it needs an updated version
I agree a manifold can lose power, but don't think a big exhaust can. There have always been high powered engines at the top of their game with no exhausts at all. As I see it it's there to carry a cat and the fumes and noise to the back of the car and reduce the noise on the way without being restrictive.
The graphs bear this out, there was practically zero difference to max bhp going from 60 to 75mm.
You can have a minimum, not a maximum.
The car came with 160bhp and a 60mm system as standard, why did they do that when they could have used your recommended 50mm? It would have saved them a lot of money and made the car lighter.
Edited by 227bhp on Sunday 12th January 11:31
Inline__engine said:
227bhp said:
I have the latest Pipemax now, it's very hard work and also has bugs in it. I'm hoping to get my head around it soon.
The problem with a lot of these programs is they depend on the paying customer to iron out the faults for them!
i just ran some numbers after i found most info except head flow. no bugs foundThe problem with a lot of these programs is they depend on the paying customer to iron out the faults for them!
what engine is this?
throwing some stuff at pipemax with guestimations suggested a duration in the order of ~230-235 at 1.0mm for both inlet and exhaust for a 250hp engine goal. and primary of 1-5/8" and 2-3/8" tailpipe. this means for something 180bhp currently its way out to lunch.
227bhp said:
The car came with 160bhp and a 60mm system as standard, why did they do that when they could have used your recommended 50mm? It would have saved them a lot of money and made the car lighter.
The factory car came with no silencers and just straight pipes ? All with nice mandrel bends ?I suspect the OEM have a little more to consider than a crude race setup.
DeadCatWalking said:
227bhp said:
, why did they do that when they could have used your recommended 50mm?
I said 2/1/2" which is not 50 mm.System O/D
Inches System O/D
MM Max Power Output
BHP
1 5/8" 41.3mm 104
1 3/4" 44.5mm 122
1 7/8" 47.6mm 141
2" 50.8mm 162
2 1/8" 54.0mm 184
2 1/4" 57.1mm 208
2 3/8" 60.3mm 233
2 1/2" 63.5mm 260
2 5/8" 66.7mm 288
2 3/4" 69.9mm 318
2 7/8" 73.0mm 349
3" 76.2mm 381
3 1/8" 79.4mm 415
3 1/4" 82.5mm 450
3 3/8" 85.7mm 487
3 1/2" 88.9mm 525
3 5/8" 92.1mm 565
3 3/4" 95.3mm 606
3 7/8" 98.4mm 648
4" 101.6mm 692
If you think the exhaust is just there to hold the muffler on you're never going to get anywhere.
FWIW I have 160 bhp from 1.6 litres, with a 2-1/4" exhaust, which lines up well with the cat's numbers.
That's a street engine with cat & muffler.
I designed the exhaust using a spreadsheet I wrote, after reading everything I could, and talking to people a lot more knowledgeable than me, and compared the numbers with similar engines as a sanity check.
A lot of US tuning books are based on 4 cyl engines being 1/2 a pushrod 2v v8, and give questionable numbers, to say the least.
FWIW I have 160 bhp from 1.6 litres, with a 2-1/4" exhaust, which lines up well with the cat's numbers.
That's a street engine with cat & muffler.
I designed the exhaust using a spreadsheet I wrote, after reading everything I could, and talking to people a lot more knowledgeable than me, and compared the numbers with similar engines as a sanity check.
A lot of US tuning books are based on 4 cyl engines being 1/2 a pushrod 2v v8, and give questionable numbers, to say the least.
AW111 said:
If you think the exhaust is just there to hold the muffler on you're never going to get anywhere.
FWIW I have 160 bhp from 1.6 litres, with a 2-1/4" exhaust, which lines up well with the cat's numbers.
That's a street engine with cat & muffler.
I designed the exhaust using a spreadsheet I wrote, after reading everything I could, and talking to people a lot more knowledgeable than me, and compared the numbers with similar engines as a sanity check.
A lot of US tuning books are based on 4 cyl engines being 1/2 a pushrod 2v v8, and give questionable numbers, to say the least.
Why when you could have fitted a 2" system?FWIW I have 160 bhp from 1.6 litres, with a 2-1/4" exhaust, which lines up well with the cat's numbers.
That's a street engine with cat & muffler.
I designed the exhaust using a spreadsheet I wrote, after reading everything I could, and talking to people a lot more knowledgeable than me, and compared the numbers with similar engines as a sanity check.
A lot of US tuning books are based on 4 cyl engines being 1/2 a pushrod 2v v8, and give questionable numbers, to say the least.
https://web.archive.org/web/20110903091024/http://...
2 1/4 is for 208bhp
Why does my 160bhp road car have a 60mm exhaust as standard when it should be 50?
No-one is looking at US V8 tuning books.
Read the first post properly and study the graphs, the bigger exhaust made from between a gain to zero loss where it matters most.
These guys need to go as quickly as possible no matter what, they have no exhausts:
Edited by 227bhp on Sunday 12th January 13:42
227bhp said:
You can't accurately model this manifold that's the biggest issue.
you don't need to in order to work out the cam and exhaust ballpark recommendations, its not a simulation. one of the outputs is the recommended runner lengths.In any case lets be real the exhaust is way oversize for a 190 bhp engine, its probably good for something 260-280 bhp and something more suitable would drastically improve the driveability of the engine but thats based on the current hp number which is clearly much lower than your expectations.
Having said that its unlikely its the exhaust side costing the top end issues and causing the power plateau (almost constant power 6000-7500) which is almost certainly inlet side related due to a restriction.
i'd be going to a proper ITB setup with a bunch of different trumpet length and remap as one way or another this is the plan anyway. once you've got the inlet working properly then you can revisit the exhaust cam and exhaust depending how close you get to the 250bhp number. what has been done to head in terms of valve jobs, porting etc is the said engine know to have a adequate cylinder head?
There is not a lot to revisit here. The engine appears to be of a common origin. It is a well trodden path with various companies having a go at improving it. Maybe there is more to give, I don't know.
If this is a learning exercise, then the best lesson is to not reinvent the wheel.
If this is a learning exercise, then the best lesson is to not reinvent the wheel.
Edited by stevesingo on Wednesday 15th January 14:25
I'm sure Peter Burgess has many experiences of overly large exhaust systems and what they do. I even remember one. It was on my own 1380 Metro with some huge bore Peco thing that killed the low down torque to where it wouldn't pull the skin off a rice pudding. I bought a super cheapo OE system about the size of a pea shooter for pennies from a factors, we cut the two restrictive OE silencers out and welded in a single straight through MGB back box. All the torque came back and no loss of top end. We actually had to sleeve down from the manifold exit to the start of the smaller exhaust system with some kind of cone thingy that was lying about.
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