PSI verses Timing Advanced

[Noddle]

Hi,

 

I been reading some post where TonyD and other are talking about not needing to run higher turbo boost pressures, but to allow the head to breath more.

 

But I have not heard anything about spark advanced verses boost pressure, for example,

 

lets say I'm running 20psi, but I can only run 10 degrees max at high RPM,

 

would this give more power than say running 12 psi running 35-38 degree at the same RPM.

 

Nigel

[BLOZ UP]

Hi,

 

I been reading some post where TonyD and other are talking about not needing to run higher turbo boost pressures, but to allow the head to breath more.

 

But I have not heard anything about spark advanced verses boost pressure, for example,

 

lets say I'm running 20psi, but I can only run 10 degrees max at high RPM,

 

would this give more power than say running 12 psi running 35-38 degree at the same RPM.

 

Nigel

 

Depends a bit on the turbo, but generally the timing is retarded to just prevent detonation. It doesn't necessarily reduce power, because the flame front will be moving faster at higher boost pressure anyway.

[Tony D]

What is have always said is boost is merely a reflection of restriction to flow. The more flow you have, the more power you make.

 

A properly ported head will make 300+ HP at 8psi of boost.

 

A stock head will need 15+ psi to make that kind of number.

 

And guess what? At 15psi you will not be able to run as much advance, due to the detonation issues. Along with a myriad of other issues (smaller plug gap to prevent misfire, blah blah blah...)

 

When people realize a car with a J-Pipe at 8psi is making 300HP while they struggle to make that same power number with 2X the 'boost' and 25 kilos of piping, intercooler, blahblahblah hung out on the furthest polar moment of their vehicle.... Well they get a bit dumbfounded and perplexed. But hey, it's what everybody in the books said to do! I mean, they are all successful businessmen selling all that kind of stuff. They wouldn't sell it if you didn't need it, right?

 

The advance number will make more power. But ultimately it's the cylinder charge that will make the power. If you have the SAME cylinder charge, there will be an advance number that is optimal to get peak cylinder pressure at the proper crank angle before TDC. The rate of burn on the fuel is relatively constant, and the higher you twist it, the further advanced you need to go to get that peak cylinder pressure at the same crank angle---this is basic physics. If you can't run that advance number because of detonation then you are giving up power retarding the spark. But that is overwhelmed by the fact you are cramming so much more fuel and air in there. You have more cylinder charge at 20psi than you do at 12.

 

Now, will you burn ALL the fuel and get the OPTIMAL pressure at full advance at 12psi? Maybe.

 

You know you aren't optimal at 20psi, but you make more power nonetheless.

 

Now, port the head so that the new cylinder filling at 12psi (maybe a more efficient turbo) is the quivalent of 20 at the old setup and you will make more power.

 

Problem is, you'll make even more power at 20psi even giving up optimum spark angle for the reasons above.

 

But making it at 12psi will result in so many different advantageous things (see some above) that yo ustart to question the 'maximum boost' theology.

 

No, you don't HAVE to port a head to make big power with a turbo.

 

But when you make 350hp/380ft-lbs of torque at 9psi.... who really needs that expensive shiny intercooler? Especially if 300HP was your goal all along?

[Brad-ManQ45]

I agree wholeheartedly w/what TonyD has said.

 

I would like to point out though, that a good port job will cost over 3 times what an intercooler setup will, and you don't have to take the head off. Once you port the head then you have a problem w/flow through the stock intake manifold.

 

For basic daily driving and occasional trips down the strip wanting 300HP w/little effort or cost just exhaust, aftermarket EMS, intercooling and upping the boost to 18/20 PSI would be the ticket - and done in that order for a variety of reasons. Let's face it - not all of it is gonna be used very often.

 

You'll need all of that stuff BEFORE porting the heads and intake will be much use.

 

But if you were to make a habit of some kind of racing, then expect to spend the bucks to be reliable AND competitive in a harsher environment.

 

Now if you had the engine apart already and have the bucks...

 

In case you're wondering about my reasoning for the order of changes:

 

Exhaust will provide more torque/boost quicker - a relatively cheap/easy mod that can and will whet the appetite for more.

 

You can up the boost to 10 PSI at this point and get about 220 HP.

 

Aftermarket EMS & bigger injectors - overall driveability and engine response is SO much better that the stock stuff.

 

Intercooler to up the boost safely to the 300 HP level.

[Tony D]

Remember the EuroTurbos came with no catalyst, a .82 A/R hotside, and 200bhp.

 

That's stock.

 

Going to a 3" downpipe and exhaust will bump that another 20-25hp.

 

At stock boost levels.

 

This is an example of 'flow on the exhaust side'...

 

So many people figure just 'cram it in there and we will make the power' (and to some extent they are correct) but just skip the fact that the efficiency of what they are doing is mind-boggling.

 

Think of the 'turbocharging is free horsepower' paradigm. Is it, really? You have 7psi of exhaust backpressure at 200HP. Wouldn't a properly ported and polished N/A return 220bhp with ease at relatively the same conditions without that backpressure? It would.

 

The turbo DOES come with a horsepower penalty due to the exhaust restriction. Thing is because of the forced induction tradeoff people don't look at that end of the equation.

 

When you realize the efficiency of an L28 making 380 ft-lbs of torque with the same intake and exhaust pressure (pre-turbine) at 7000+ rpms you start seeing the 'turbo lag paradigm' for what it really is: inappropriate component selection and compromise.

 

They weren't making 1795HP out of 1.5 Liters in the early 80's Honda F1 Engines by corking the exhaust and intake...

 

There's a better way to turbo a car, and you get a totally different driving experience than what the 'old school turbo gurus' will preach to you.

 

I, for one, find this type of build extremely rewarding!

[Noddle]

This is an example of 'flow on the exhaust side'...

 

I assume a 3 inch mandrel bend exhaust with no cat, and a free flowing muffler should make it breath easier,

this is what I have been been running since I started playing with my turbo charger and EFI ( MSII ), talk about a steep learning curve.

 

 

What can be done to a standard turbo manifold to make it flow better ?,

 

I've been working on mine, mainly on the area inside the mouth of the runners, removing the rough casting, and opening it a little.

 

Nigel

Edited September 7, 2010 by Noddle

[cygnusx1]

This is very close to sticky material. Great stuff.

[Brad-ManQ45]

Still agree w/ everything TonyD has said.

 

Noddle:

 

I port matched my exhaust manifold to the gasket - same as the head - didn't want to open up the ports further.

 

Then I smoothed the inside of the runners as much as possible.

 

I also port matched the turbo inlet on the manifold to the gasket - as well as the turbine housing inlet.

 

Lastly, I bought a pencil type air grinder and a few carbide burrs and started opening up the manifold from the front 3 or 4 cylinders into the plenum for the turbo inlet. There is a lot of casting flash in there that I could feel. I didn't open it up a whole lot, but every little bit helps and there are no ridges or flash left.

 

This can only help the flow.

 

Now if I had a euro manifold - it would be a lot easier to do this to...

 

I

[JSM]

Tony,

 

I'm curious to see where cost comes in at this? From the research I've done it's close to $1200 for a decent head job? Is the head job more cost effective in the long run in comparison to an intercooler and some piping with more boost?

[Calgary280ZT]

Tony has made his boost argument before and I drank the Kool aid. So when I built my car I opened it up as much as I could with the budget I had. You can see my mods in my sig. Now I can attest to the truth of what Tony is preaching. The car makes around 325 rwhp at 10 psi. I've had a couple of members on here look at my timing map and everyone agrees its pretty conservative. It probably wouldn't be difficult to get to Tony's 350/380 numbers with a little dyno tuning, which we hope to do in the very near future. Yes, it cost me some $$, but if I had to do it again I would do the same thing.

 

JSM: Rebello charged me $1000 for his "race port." The head had originally been prepped by Rebello with an Isky cam, big SS intakes and the beginning of a port. I bought it for $400 never intalled, I imagine it cost the owner $800-1000. My cheap Chinese IC cost me $150 max. Piping and couplers was perhaps the same, but I could never get the damn stuff to stay together...very annoying to have an IC piping leak you can't find when you're 2800 kms from home. The SS IC piping cost me $550 in material and my mechanic swapped a big brake Z32 kit for the labour and I swapped him video....probably would have been another $400-500. So the IC is a cheaper route to go than the head (in my experience), but I'm glad I did both.

Edited September 9, 2010 by Calgary280ZT

[Tony D]

Tony,

 

I'm curious to see where cost comes in at this? From the research I've done it's close to $1200 for a decent head job? Is the head job more cost effective in the long run in comparison to an intercooler and some piping with more boost?

 

As you see from Markham's post, 'intercooler cost' is no longer an issue. So the question becomes run 20psi and retard the hell out of the timing, or run 10 with full advance and the benefits.

 

Really, there was a time when a good spearco or brand-name intercooler would cost you as much or more than the head porting.

 

And give you what? Density increase?

 

Markham is making 300 HP (thereabouts).... Think about this at 10psi.

 

Do you need to run premium gasoline at that particular boost level?

Do you need to run an intercooler?

 

Things that become mandatory at 20psi are not necessary at 8-10 psi.

 

Remember the stock turbo ran no intercooler. If you get a bigger, more efficient turbocharger that has the same discharge temperature (due to efficiency) at 10psi at a 300HP flow rate, and have a head that will FLOW that same number, you end up with intake charge temperatures of a STOCK turbo engine with the FLOW of 300hp.

 

Meaning no intercooler is required.

 

Now, most of you don't have to go through smog...but...think about the 'stealth' advantages.

 

People say you MUST have an intercooler to make horsepower. No, you don't. Not if you have low enough temperatures. There is a point where charge cooling will become necessary, but for the VAST majority of people below 350HP, there is actually no reason to bother with it if you think about it from the beginning.

 

Some of these engine bays are not the most conducive for plumbing a lot of piping (think ZX's!) Running that kind of HP is entirely possible un-intercooled. Sure, you pick up efficiency, but it's not the requirement that everybody says it is.

 

I mean, I know plenty of guys who have 250HP ZX's with these big honking intercoolers up there.

 

WHY?

 

As to the stock manifold porting, take a look at JeffP's Extreme 280ZXT page, he's got some good photos of the before and after porting of his manifolds as I recall. Really, up to 500HP there doesn't seem to be much of a need for 'more than the stocker' there, either.

 

It's just too much reading of theoretical books by people with parts to sell, IMO.

[Noddle]

As to the stock manifold porting, take a look at JeffP's Extreme 280ZXT page, he's got some good photos of the before and after porting of his manifolds as I recall. Really, up to 500HP there doesn't seem to be much of a need for 'more than the stocker' there, either.

 

http://www.angelfire.com/extreme/280zxt/page11.html

[Noddle]

Tony,

 

I found this while doing some searching, I assume it has not moved on, from been a good ides ?

 

 

http://forums.hybridz.org/index.php/topic/79968-euro-manifold-in-ss-316l/page__view__findpost__p__761294

 

Turbo location is the same. Ports are the same. The main difference is that the manifold is a three piece affair meant for continuous boost, it utilizes expansion joints to keep the manifold from warping and shearing the studs, as well as accomodating more flow internally. The Euro Cars used the same turbo, with an .82 A/R, and were rated at 200HP instead of 180. No Catalyst, no EGR, no ECCS, Pneumatically Retard Module on an E12-80 Conventional Distributor.

 

When Jeff got his SFP Tubular header, I kind of snickered, and then pulled out my Euro Manifold. First Jeff looked really closely. Then he got the caliper. Then he started swearing a lot. I mean, a REAL lot! The stock Euro Manifold was larger internally than the 1 5/8" SFP Tubular Header!

 

Well, didn't swear as much as he did when he found out most Nissan Manifolds were cast in steel and were weldable, so he could modify the externals to accomodate an external wastegate... I ended up packing one in a suitcase that last time I visited Frank 280ZX. (Like the Differenital Cooler) I think he has several photos of the unmodified manifold on his webpage 'Extreme 280ZXT'...

 

I took a look at Jeff's modified Euro Manifold, it looks good. I think with some little tweaks, we could get a local foundry to look into casting it up. I will have to PM Derek and get some suggestions for people he knows in the biz if I can't find a place locally that has suitable foundry facilities. This has the potential to be a very cool piece when done.

 

 

I did some measurement today on the thickness of my manifold, where the runners squeezes together, its about 4mm thick, so I wont be doing anything like JeffP did.

 

Nigel

[Tony D]

Costs for even prototyping were more than most people have in their cars.

 

My backyard foundry is not something I can get into at this point, so we won't be cutting up our Euro Manifolds or making any in Stainless Steel.

 

If you want one, you will have to get one from Europe, same as the rest of us!

[Calgary280ZT]

Here's another question for Tony: the only engine component not modified or upgraded is the exhaust manifold. Bone stock. Am I losing hp/torque or driveability? At what point is it worth working on the exhaust mani? 350 hp? 500 hp?

 

The downpipe is currently 2.5" (not sure how anyone gets 3" on the turbo, there just wasn't enough room when we were fabbing up the DP) emptying into a mandrel bent 3" system. No cat....yet.

[rossman]

Jeffp was putting out over 650 HP on a modified stock manifold. Couple that with the fact that the stock manifold is much more robust than most (all?) L6 turbo headers. I ended up selling my custom turbo header for those very reasons.

 

I didn't ported my exhaust manifold as much as Jeffp. I opened up the turbo flange area as much as I could. There quite a bit of material in that location. At the exhaust ports I was afraid of thinning out the runners to much, creating hot spots and cracking. I just knocked off the high spots, smoothed out the transitions and called it a day.

 

This thread is making me think twice about installing an intercooler. I personally don't care for intercoolers hanging off the front end and it sure would clean up the engine bay without all that piping going everywhere. Hmmm, decisions, decisions.

[cygnusx1]

No matter how you slice it, an intercooler is good insurance with direct benefits.  Even with a holy-grail head its a good thing.

[Tony D]

Cygnus, run me a test at 8psi and show the benefits of an intercooler versus not having one.

 

Then do it at 10psi.

 

Then do it at 12psi.

 

IF YOU DON'T GENERATE THE HEAT, INTERCOOLING (while THEORETICALLY advantageous) IS NOT REQUIRED!

 

Read the above quotes and show me HOW MUCH you GAIN from an intercooler on 8psi. There are MILLIONS of non-intercooled OEM fitment vehicles out there...with 100,000+ mile reliability. Are you saying they are all defective designs?

 

Engineering takes reasoning, not rote memorization of a set of components.

 

Show me any place (even in the much vaunted "Corky Book") where intercooling is mentioned for ANYTHING below 12psi.

 

If you have the flow, don't have the heat, the increase in density in marginal at best. For the bother, a 2 gallon methanol kit can be installed with FAR GREATER advantages for as much as you use boost.(Lets look where the CG of the installed components would be, for instance...) A 2 gallon meth kit on a 10 or 12psi setup (even 15psi) would last two tanks of petrol to one fill of anti-detonant. If filling oil on your oil injected two stroke is not a big deal, filling your water tank isn't either.

 

If I can make 350HP UNINTERCOOLED in 1985, on carburettors.... I'm thinking with the advances in methanol injection and EFI it should be even easier today.

 

40,000+ miles and I'm still on the original head gasket. Better than I can say for many WITH an intercooler in the same horsepower range...

 

Thinking gains dividends. Following the pack means your view never changes unless you're the leader.

Edited September 12, 2010 by Tony D

[Calgary280ZT]

Rossman, did you notice any difference in power or driveability? At this point I'm thinking my time and money is better spent elsewhere....

 

Jeffp was putting out over 650 HP on a modified stock manifold. Couple that with the fact that the stock manifold is much more robust than most (all?) L6 turbo headers. I ended up selling my custom turbo header for those very reasons.

 

I didn't ported my exhaust manifold as much as Jeffp. I opened up the turbo flange area as much as I could. There quite a bit of material in that location. At the exhaust ports I was afraid of thinning out the runners to much, creating hot spots and cracking. I just knocked off the high spots, smoothed out the transitions and called it a day.

[dhartig]

IMHO most people like intercoolers because they are a KISS system, bolt it on and forget about it as you adjust your EBC. To be optimized meth injection requires progressive control , and a fail safe to drop boost if flow is interupted.

 

But a meth system would seem to be more in line with the goal of having a well breathing engine.