Jeep Strokers

Dino, Silver and myself started a bit of conversation in another thread on compression and factors contributing to the limits. Mainly discussion Static Compression Ration (SCR) and the effects of;

Fuel type and blend.
Heat of incoming charge.

For this conversation let`s assume we are running with a zero deck and a .043 (+/-) quench.

Lets try and list some of the variables (not mentioned above) and what we can do to nullify or promote each on it`s own merit.

I`ll throw thoughts out that hopefully can be expend on with proven fact. Not just opinion or hearsay.

Would insulating the header help to reduce heat transfer to the intake manifold ? Upside/downside too ?

Moving the IAT sensor from the intake manifold to a remore location upstream towards the airfilter "fool" the ECM into adding a richer mixture and more timing ? Does the IAT have an effect on timing or is it only mixture ?

Coatings to the combustion chamber/piston crown/intake manifold.

Spark plug location and tip orientation to the ports/valves.



There are some good knowledge folks on this site that may be of help.
http://speedtalk.com/forum/

I can tell you from my own experience that adding a heatshield to the underside of the intake manifold does reduce intake runner temp. by reflecting away radiant heat from the header. Anything you can do to reduce the intake charge temp. is a good thing (make sure your cold air intake is indeed a cold air (not hot air) intake).
Coatings to the combustion chambers and the piston dishes have certainly been proven to reduce detonation risk.
Relocating the IAT sensor to a cooler location does fool the engine computer into advancing the timing and enriching the A/F mixture but the effect is small.
Fuel type and blend certainly have some influence, as some additives (e.g. MTBE, ethanol) can raise the octane rating. Propane and ethanol allow higher SCR's to be used without detonation.
I'm sure there's a long list of other things I can't think of at the moment.

Cheromaniac wrote:I can tell you from my own experience that adding a heatshield to the underside of the intake manifold does reduce intake runner temp. by reflecting away radiant heat from the header. Anything you can do to reduce the intake charge temp. is a good thing (make sure your cold air intake is indeed a cold air (not hot air) intake).
Coatings to the combustion chambers and the piston dishes have certainly been proven to reduce detonation risk.
Relocating the IAT sensor to a cooler location does fool the engine computer into advancing the timing and enriching the A/F mixture but the effect is small.
Fuel type and blend certainly have some influence, as some additives (e.g. MTBE, ethanol) can raise the octane rating. Propane and ethanol allow higher SCR's to be used without detonation.
I'm sure there's a long list of other things I can't think of at the moment.

With respect Dino, these are not the answers we are looking for. I want to raise this thread above the standard "lawnmower" engineering and move it ahead.

While I agree cooling the intake manifold is a good start..........But how ? Is there a heat reflecting coating ? A simple heat shield ? What are the pro`s and con`s of wrapping the header ? If you did wrap the header how much heat would be retained ? What effect would it have on engine efficiency ?

How about this stuff ? http://www.summitracing.com/search/Prod ... ord=thermo

Moving the IAT fools the engine. But by how much ? Numbers we want numbers at degrees of temperature.

Fuel blends do play a big part. MTBE releases oxygen upon combustion. Bad choice for a hi SCR. Yes Propane raises the compression you can run but propane carries less BTU energy.

jsawduste wrote:While I agree cooling the intake manifold is a good start..........But how ? Is there a heat reflecting coating ?

Jet hot or some of its comepitors does that.

A simple heat shield ?

A piece of steel or aluminum would make for a good start

What are the pro`s and con`s of wrapping the header ? If you did wrap the header how much heat would be retained ? What effect would it have on engine efficiency ?

Haven't had any experience but I have heard that it does mak ethe engie more effiecent .. why escapes me now. It does keep heat in the exhaust and away from the intake. And its cheap. However, it can hasten the pipe cracking and rusting.

How about this stuff ? http://www.summitracing.com/search/Prod ... ord=thermo

I tried that stuff on a clean manifold. It didn't stick quite well. And it burns when it contacts the header.

jsawduste wrote:While I agree cooling the intake manifold is a good start..........But how ?

POLISH it, it'll act like a mirror and reflect the heat, a tin sheild between it and the heaader will help too!

jsawduste wrote:I want to raise this thread above the standard "lawnmower" engineering and move it ahead.

Moving the IAT fools the engine. But by how much ? Numbers we want numbers at degrees of temperature.

If you want to get beyond "lawnmower engineering", then you're going to have to talk about *REAL* engine management. "Fooling" sensors is not real engine management. Adjusting the timing tables to give a high compression engine what it really needs or wants is real engine management.

TheDarkSideofWill wrote:

jsawduste wrote:I want to raise this thread above the standard "lawnmower" engineering and move it ahead.

Moving the IAT fools the engine. But by how much ? Numbers we want numbers at degrees of temperature.

If you want to get beyond "lawnmower engineering", then you're going to have to talk about *REAL* engine management. "Fooling" sensors is not real engine management. Adjusting the timing tables to give a high compression engine what it really needs or wants is real engine management.

No doubt, if you can show us how to change the timing tables of an OBD 1 ECU we are all listening. Need a baseline first and understanding of the OEM set up first.

Yes we could use a stand alone management system. Ultimately that could be the answer. But even folks (Silver for instance) who has an Apexi has not been able to break the mid 9`s in compression.

However

Without knowing the stock tables(fuel/timing) and the effect of the sensor(s) how are we to say for certain a different curve might help ? What happens when an water or air temp sensor reaches a parameter ? Does it richen the mixture ? Pull timing back ?

At best, without this knowledge all we can do is to nullify heat transfer and adjust our build accordingly.

I`d like to see what other options that are out there. Could there be a OBD 1 ECU from a different model or year have a different curve ?

Plus I would say that a 9.5 (+/-) in todays world doesn't constitute much of a hi compression engine.

Standalone engine managment would be nice, but not many people are willing to spend $1,500-2,000 on one then spend another $1,000 to get it dyno tuned.

Then you have the issue of the people who have to go through emissions testing (Small % i think), and the other issue that if you change the ECU you have to come up with the proper signals for the TCU( Transmission control unit). Older TCU units read the signals directly, but the newer ones get some signals over the CAN bus from the ECU.

So what you need is a ECU you can purchase from the junkyard for next to nothing and it would also need to have tuning software available for it. Alot of guys have used the GM TBI units on older cars becaus it is cheap and tunable. Of course these units were not port injection. Maybe we should be looking at adapting the GM V6 ECU for use with our engines. EFI LIVE has software that totally opens the tables up. It is also a MASS Air system which should be eaiser to tune then the current Jeep system. The ECU would also have a ODB2 port to address the emissions issues.

Peter, that is the kind of thinking I`d like to see on this thread....Out of the box per`se. The subject has been beat to death but little forward motion has acheived.

The GM ECU would be a great idea. Now knowing that we could open it up to whatever tables and values we wished.

OK, let`s pretend Peter could flash any values into the controller. That could take care of timing and fuel mapping.

But the fact remains, why are we limited to 9.5 squeeze ? There needs to be a underlying reason that needs to be understood first.

I'm in Iraq right now, but when I get back next July I'll be working on a distributor that will house the GM magnetic reluctor pickup that provides the trigger signal to the '7730 computer from a 90-92 Camarobird. The $8D code mask for distributor V8's has been hacked to hell and back and can be made to do anything you want.

An alternative is Megasquirt, which is cheap but much more simple-minded than any OE ECM would be.

To use a modern ('05+) GM computer, all you need is a 58 tooth reluctor wheel. That pattern shouldn't be hard to put into a flywheel or flexplate.

An ECM doesn't have a "curve" like a distributor... it has a table, which is a collection of different curves. One axis of the table is MAP, which would be manipulated by vacuum advance on a non-EFI distributor. The other axis is RPM, which is similar to mechanical advance in an old distributor. The important thing that EFI can do that a distributor can not is change the timing at ONE point on the table (one value of RPM and one value of MAP) WITHOUT changing any of the others.

So if you experience ping between 50 and 60 kPa MAP at 2500 RPM, then you can reduce timing at that point only, without affecting any of the table surrounding that point.

On an ECM like the '7730 with reasonably capable knock detection, you can also tune the sensitivity of the knock detection, the amount of timing the ECM pulls when it detects knock and how fast the timing is put back once the knock stops.

As far as how to build an engine to avoid knock... there's not much you can do if the heads available all have crappy chambers and poor ports that don't yield good mixture motion. Is there one head that's more knock prone than the others?

I read a topic here on this forum that said that the chambers overhang the bores in any stroker. This isn't good, as that is a large amount of crevice volume to promote poor combustion.
Also, any amount the piston comes out of the hole is going to promote poor combustion by increasing crevice volume via the bore in the head gasket being larger than the bore in the block. The head gasket should be as thin as possible with the gasket bore as close as possible to the block bore.

Quench needs to be *TIGHT*.
.040 is the desired number.
.060 will be ruinous for detonation resistance. If you know you have .060 quench, don't even talk about how much your engine knocks. We already know.

Ceramic coatings supposedly help. I'm just starting to play with them on other engines. I'll certainly use them on the pistons when my stroker goes together. They're not hard to apply to the head at a later date.

jsawduste wrote:Without knowing the stock tables(fuel/timing) and the effect of the sensor(s) how are we to say for certain a different curve might help ? What happens when an water or air temp sensor reaches a parameter ? Does it richen the mixture ? Pull timing back ?

This is still lawnmower engineering. Imagine trying to dial in an engine in a classic muscle car while only being able to change the jets and fuel pressure, but being unable to change the metering rods or the mechanical advance or the vacuum advance or the accelerator pump. Do you think you'd ever get the engine to run right? No, you wouldn't... yet you expect to be able to do exactly that with an EFI engine and have it run perfectly.

You must accept that you can not bring an engine to its full potential without modifying the ECM. You must accept that without retuning the ECM, you will be limited to mediocre results. If you want to put something together that runs well enough, that's fine. If you want to push the limits and go beyond lawnmower engineering, you'll need real engine management.

jsawduste wrote:Peter, that is the kind of thinking I`d like to see on this thread....Out of the box per`se. The subject has been beat to death but little forward motion has acheived.

The GM ECU would be a great idea. Now knowing that we could open it up to whatever tables and values we wished.

OK, let`s pretend Peter could flash any values into the controller. That could take care of timing and fuel mapping.

But the fact remains, why are we limited to 9.5 squeeze ? There needs to be a underlying reason that needs to be understood first.

Well you vcould probably go to 10.5 without a problem by using the Hesco aluminum head. Is the gain worth the pain ($2,000?)

I do not think you will get a good answer, If you want real engineering, then someone has to put the time in to R&d with different types of fuels and different operation conditions to come up with a real answer. It seems that the majority of the people that install strokers do not bother to do much with tuning, they are happy with what they get.

I am not aware of any professional engineers on the board doing R&D on the combustion cycle of the Jeep inline 6. However we are all doing R&d on somewhat of a trial and error bassis. ( lawnmower engineers)

So the only way to get an answer with the currently avail data pool is to ask people about their buils, what type of fuel they run, what altitude they live at, what is the air temprature in the summer, ETC. Then take this data and compile it and see what works.


As for the 9.5 cr limit for regular gas, this seems to be a fairly common number in the auto industry, Aluminum heads let you run a higher CR, but everybody knows that. What is your target? 9.7? 10.0? Is it a big deal if i can run 9.7 instead of 9.5? Why not just run E85, you can run 11:1 then.

The bottom line is that we have an engine that was designed in the middlle of the 1960's and has not changed much since. The engine control electronics have added allot of capability to the engine, but they have not changed very much since 1994. (15 years ago)

The real solution the the exhaust heat getting into the intake is a cross flow head. Heat shields are a good idea and i would like to see someone dyno their truck without a heat shield than add one on and dyno it again. What do you think you will get? 10hp? 5? and by doing this , how much will it allow us to increase the Compression ratio?

How about this for a solution, rip out your ODB1 or ODB2 unit and put a Renix in. It has a knock sensor and will retard the timing automatically.

Mr. Dark and Mr. Peter bring some interesting comments to the forefront.

Again, my hope for this thread is that we can all (factually) learn what the demands of optimizing a properly built I6 stroker. By using the word "optimize" it is meant for building, tuning and using your stroker for how YOU intend on using it. In no way would I expect a "one size fits all" solution. You simply cannot harness all the variables. We can however, identify and build our engines (and expectations) around proven and given facts. Which sadly are all over the page when it comes to Jeep stroker engines.

The many variables in both mechanical and tuning as Peter and Mr. D have pointed out are only the tip of the iceberg. Some things, like quench for example, are based on proven fact and can be applied to most any engine. You simply cannot fool with the laws of physics as it applies to combustion and achieve optimum results.

While there are plenty of folks who are happy with their low buck/high quench engines, thanks for pointing that out, Peter. The flip side, their is always a group of folks that are looking for ways to compliment and enhance there engines performance. Be it to run on low octane fuel or achieve out right power.

Unfortunately as Peter has pointed out. Not much has been done in the way of improvements on the I6 in many years. However, technology has continued to move on. What we need are folks (like Mr. D) whom are more up to speed with today’s modern technology and help us to incorporate it into our beloved and neglected strokers.

Sound of soap box skidding across the floor............

In simple terms, no matter how we build our engines we are all limited to some common but basic constraints. A short block that has proven reliability but has a relatively low rpm threshold. An intake and exhaust that share common ground. Ports, combustion chambers, and valve shrouding that date back to the Stone Age. Camshafts that seem more like afterthoughts to the major grinders. Intake manifolds that are at best controlled leaks rather then effiecnt means of evenly distributing fuel.

Can we as a group attack each of these items and try to not only educate ourselves but also educate the aftermarket also ?

Case pinpoint. The Hesco aluminum head. While questionable on a stock engine. The enhanced heat dissipation has allowed for bumps in compression. What else is different ? Are the ports better ? Is the combustion chamber designed different ? Are there any ideas we might be able to apply to our iron headed engines ?

How about long vs. short rod engines ? Does the increase dwell time at TDC have an effect ?

IIRC Lunati is the only company offering up cams with steeper then normal intake ramps.
Header wraps, seems like a touchy subject. It would seem that any way we could minimize heat transfer to the intake. But some folks say the down side is not good, why, because my header will not last as long ? Why not ?

Let’s all do some research. Get facts, try some ideas. Share our facts and let’s try to bring our I6 into the next generation. The information is out there. We just need to harness it all in.

jsawduste wrote:While I agree cooling the intake manifold is a good start..........But how ? Is there a heat reflecting coating ? A simple heat shield ? What are the pro`s and con`s of wrapping the header ? If you did wrap the header how much heat would be retained ? What effect would it have on engine efficiency ?

How about this stuff ? http://www.summitracing.com/search/Prod ... ord=thermo

I'm glad you mentioned the Thermotec heat barrier 'cause that's exactly what I stuck onto the underside of my intake manifold. Here's my write-up:

http://www.angelfire.com/my/fan/manifold.html

As far as wrapping the header goes, it's the most effective way of all to reduce underhood heat but has the cons of trapping in moisture/heat around the header tubes. The moisture increases the risk of corrosion and the heat makes the header tubes more brittle, so both will shorten header life.

jsawduste wrote:Moving the IAT fools the engine. But by how much ? Numbers we want numbers at degrees of temperature.

The only way to find out is to datalog these parameters from the OBD 1 computer. Not an easy task.

jsawduste wrote:With respect Dino, these are not the answers we are looking for. I want to raise this thread above the standard "lawnmower" engineering and move it ahead.

I see your point but we're all "lawnmower engineers" 'cause none of us have sophisticated R&D facilities in which to properly conduct engineering research. Bennie Fulps at Hesco does and his knowledge of the Jeep I-6 engine is probably second to none. Peter described our situation quite eloquently:

Plechtan wrote:However we are all doing R&d on somewhat of a trial and error basis. ( lawnmower engineers)
So the only way to get an answer with the currently available data pool is to ask people about their builds, what type of fuel they run, what altitude they live at, what is the air temprature in the summer, ETC. Then take this data and compile it and see what works.

OBTW, what's "regular" gas? Running 9.5 on 87 octane under an iron head isn't too bad. Not being able to run 9.5 under an iron head on 93 is pretty bad.