To Cat or Not to Cat??

[1batt4u]

Hi all,

I rememebr reading, without the catalytic converters the Delorean has around 170HP. Sound right??

I am in the processs of changing the whole exhaust system, are the cats really necessary?? I live in New York so the cats are not mandatory.

What do you guys recommend??

Thank you!!

[opethmike]

No way there is a 40 HP gain from going cat-less.

[TTait]

You will notice a performance boost without the cat - I ran a hollow cat for more than a year until I had to get smogged again.

[DeLorean03]

I dont have a cat on mine, and there's no way I am getting 170 HP. Maybe 140-145 at most.

[WelmoedJ]

Removing a cat gets you an additional 12 HP at the most.
The 160 HP power is only found in European versions of the PRV.
The US version, without cat will reach about 140-142.

Mind that these figures only refer to SAE (crank) HP, not wheel HP!

Dyno (wheel) figures go from some 90 (auto) to some 110 (manual) for our standard DeLorean engine.

[DMC3165]

Hi all,

I rememebr reading, without the catalytic converters the Delorean has around 170HP. Sound right??

I am in the processs of changing the whole exhaust system, are the cats really necessary?? I live in New York so the cats are not mandatory.

What do you guys recommend??

Thank you!!

Where we live any vehicle that's 25 years old or order doesn't have to pass emissions anymore (but you already know that). I think our motors can be set up to produce 170 HP but not with stock settings (timing, fuel pres, maybe cams not sure). My exhaust is bone stock with Cats. It's still in good shape so I'm leaving it until I need to do something. I'll probably go with a stage 1 from DMCH or a Hervey setup. I'll see when the time is right.

[TTait]

Where we live any vehicle that's 25 years old or order doesn't have to pass emissions anymore

Not in California I'm afraid. We have to pass every 2 years and before we can sell it...

Any car after 1977 has to pass here, and that date is no longer rolling, it sticks...

I enjoyed not having a cat for a while - the gain was similar to what I have now with Stegers cams. If the cat wasn't so hard to bolt up to the muffler I would probably swapped my hollow cat back on and only installed it for the smog tests.

[content22207]

... I think our motors can be set up to produce 170 HP but not with stock settings (timing, fuel pres, maybe cams not sure).....

Not unless you're planning to replace the pistons too -- Euro PRV's are 9.5:1 compression. Fueling is commensurately different as well (you could probably create a reasonable facsimile by running the frequency valve open loop). Euro CPR's have the same final control pressure as North American units, but they start lower and take longer to get there (with no Lambda to contend with, they run rich the whole time manifold pressure is down). Richer overall fuel metering allows a slightly more aggressive spark advance curve (base timing is actually retarded from North American spec: 10 degrees BTDC).


Bill Robertson
#5939

[A Van]

152hp at the flywheel, 119hp at the wheels, stock fuelling with UK performance exhaust.

We have a few guys who have fitted the Euro fuelling with DeLorean engine, one guy with such a set up and a UK exhaust, got 158 and 124 respectively.

[DMC3165]

I don't want to misquote anybody but someone should ask Justin Mettee about his car. I think he said he's making about 190 HP on a stock bottom end. I don't remember what's been done to it aside from cams and exhaust.

[A Van]

Sadly Gez who has euro block, with performance exhaust and cams couldn't make the dyno in time, it would have been interesting to see what he would have got.

[content22207]

Volvo's production camshafts and valves are identical between Euro and North American engines (increased power comes from the bottom end):
2918 2917

Bill Robertson
#5939

[A Van]

Agreed Bill, Gez has different cams however that are designated 'performance'

[jerzybondov]

Yes, my car has a euro block with reprofiled cams (the originals, but reprofiled to 272 degrees) and the UK stainless exhaust. Had a few running problems at Eurotec when the dyno was around but seriously considering making a special trip up to it to see what mine is putting out... (and what running problems may still be in the mix!!)

Also worth pointing out that before the engine swap the car put out 150.3bhp at the flywheel with a stock block, euro fuelling and UK stainless exhaust (same spec as the 158bhp car but with a B28F ignition dizzy rather than the 158bhp car's euro dizzy).

The answer to the OPs original question would be that removing the cat is likely to liberate 15bhp tops, not 40 :D

[DeloreanJoshQ]

One other thing to consider, and maybe others that have no cats will agree is the fuel smell you get without the converter when in the garage, on your clothes, in your eyes, etc. I had my cat swapped with a "cat-delete pipe" and experienced all of these symptoms. When I switched the exhaust to the DPI Spec 1 exhaust with cats, all of the smell-related issues went away...to me it wasn't worth the extra 10-15hp increase...though the Spec 1 exhaust has performance converters...

Josh Q

[Nicholas R]

I'd like to know how everyone is getting such high HP. We've dynoed many cars here with different exhausts, (hervey, stock, UK, custom exhausts) and I'm dont think any have broken 110hp at the wheels.

My automatic with the UK cat-free exhaust did 99.7hp at the wheels. (not even 100!)

I have to say, without modifying something else (cams, heads, etc), I cant see anyone getting more than 115hp at the wheels.

[Bitsyncmaster]

One other thing to consider, and maybe others that have no cats will agree is the fuel smell you get without the converter when in the garage, on your clothes, in your eyes, etc. I had my cat swapped with a "cat-delete pipe" and experienced all of these symptoms. When I switched the exhaust to the DPI Spec 1 exhaust with cats, all of the smell-related issues went away...to me it wasn't worth the extra 10-15hp increase...though the Spec 1 exhaust has performance converters...

Josh Q

My CAT is just a shell and I never noticed any change with the exhaust smell.

I think it's common knowledge to get more HP from and engine you need to run a richer AFR then 14.7. Somewhere in the low 13 range. So open loop or wideband closed loop.

[content22207]

I'd like to know how everyone is getting such high HP.

1) Higher compression
2) No Lambda / Richer overall metering
3) More aggressive spark curve
4) One would hope better ignition

Bill Robertson
#5939

[dmc6960]

Some also have different fuel venturis to get a different fueling curve, not just set richer.

[content22207]

Higher compression engines have to be run richer or they will detonate. That is why American manufacturers dropped compression across the board in the early 70's -- to decrease fuel consumption.

Unfortunately lower compression also equates to lower power.

Bill Robertson
#5939

[1batt4u]

I don't want to misquote anybody but someone should ask Justin Mettee about his car. I think he said he's making about 190 HP on a stock bottom end. I don't remember what's been done to it aside from cams and exhaust.

Here is a clip of Justin's exhaust sound! http://www.youtube.com/watch?v=OrOBCZWM8Zc
I really love this sound, I want to do the same thing.
He is using John Hervey's Performance catalytic converters and a Flowmaster Series 80 muffler.

That is the only exhaust sound I am satisfied with!!!

[A Van]

I'd like to know how everyone is getting such high HP. We've dynoed many cars here with different exhausts, (hervey, stock, UK, custom exhausts) and I'm dont think any have broken 110hp at the wheels.

My automatic with the UK cat-free exhaust did 99.7hp at the wheels. (not even 100!)

I have to say, without modifying something else (cams, heads, etc), I cant see anyone getting more than 115hp at the wheels.

We have a few cars which have made over 115 to 124 at the wheels, most are around 105-112, the ones that have reached those figures tend to be well driven and maintained well, plus we have fuelling adjusted to correct pressures as per manual using shims (if required) in the distributor this has been shown to make a considerable difference, when dynoing at Eurotec on several occasions a car has gone on, then after a pressure adjustment and tune has then increased by 8-10hp

[ramblinmike]

The '80s were a bad time for cars, weren't they? I'd love to have a free-flowing exhaust from Hervey, DMCH, DPI, etc. but I'd be embarrassed for anyone to hear it. A stock 8.8:1 2.8L PRV sounds, well, not good. Add in the valve train noise that many of our cars have and the end result doesn't exactly scream, "performance". Reminds me of what the early '90s GM 3.1L cars sounded like under acceleration. Kind of a pukey-burble sound.

I used to laugh out loud at the scene in BTTF 1 when the car is started for the first time and backed out of the trailer. That is an exhaust sound I'd show off. That laugh has since morphed into a sad face.

If only....

[content22207]

You're never going to get a smooth exhaust tone at idle from a Pre-B280 PRV because of the dead spaces in the firing order. Dual exhaust just magnifies the effect. Sounds OK at speed, however.

Bill Robertson
#5939

[Nicholas R]

1) Higher compression
2) No Lambda / Richer overall metering
3) More aggressive spark curve
4) One would hope better ignition


You can't just change the compression of an engine though; unless the seals are shot, that's all going to be determined by the volume of the cylinder which on all of our cars is the same.

Most of the dynoed cars run open loop with the mixture set at the optimal power ratio. An exhaust gas analyzer is always used for setting the mixture and during dynoing.

Everyone keeps clean properly gaped spark plugs, 8mm wires, nothing abnormal in ignition. Maybe one person has the nology setup.

Better ignition? In what way? Thats a little ambiguous.

I'm not trying to put anyone down or say that anyone is lying about their numbers, I'm really just wondering. From what I've read, I'm assuming the high numbers are coming from people with almost completely stock engines with a different exhaust. If its true I REALLY want to know how, because I honestly cannot tell people that my car has more than 100hp at the wheels, even with the UK exhaust.

[content22207]

Eurospec B28's run taller pistons than North American series (65.3mm versus 62.8 mm). That's where their increased compression comes from. I'm pretty sure heads are identical.

Bill Robertson
#5939

[content22207]

Eurospec versus North American pistons:
2922

Bill Robertson
#5939

[Nicholas R]

No way! Was the piston usage based on the original destination of the car? I never knew that the European engines used different pistons.

[Bitsyncmaster]

No way! Was the piston usage based on the original destination of the car? I never knew that the European engines used different pistons.

The Delorean engines are all the same. It's the European B28?s that may have been built for higher compression.

[content22207]

No way! Was the piston usage based on the original destination of the car? I never knew that the European engines used different pistons.

Absolutely. This is the only thing Martin Gutkowski and I agree upon.

That most European B27/B28 (and their Renault and Peugeot counterparts) are 9.5:1 compression is pretty common knowledge.

On Page 9 of this 1981 European Volvo sales brochure you will find published B28E specs (9.5:1 compression, 155 HP @ 5,500 RPM): http://www.volvoclub.org.uk/pdf/brochures/Volvo1981.pdf.

Bill Robertson
#5939

[DMC3165]

Here is a clip of Justin's exhaust sound! http://www.youtube.com/watch?v=OrOBCZWM8Zc
I really love this sound, I want to do the same thing.
He is using John Hervey's Performance catalytic converters and a Flowmaster Series 80 muffler.

That is the only exhaust sound I am satisfied with!!!

I saw Justin's car at the DMA SS this year and i thought it sounded pretty sweet!! We talked about what he had done to it and the general consensus was it was producing around 190 hp,

and sounded pretty good doing it. :biggrin:

[jmettee]

I haven't yet gotten my car dyno'd "post cams", but I had 130 HP at the wheels on stock engine with the Hervey performance CAT & the Flowmaster Series 80 (stock exhaust manifolds & crossover pipe). While I find that hard to believe from just an exhaust system, Josh Q. found out that the same setup, but with stock muffler produced little-to-no power. The CAT is restrictive & the muffler is HIGHLY restrictive.

The cams made a big difference, but I won't claim 190 HP (crank) until I install headers & back it up with a dyno. For now (pre-header), my butt-dyno estimates I probably picked up 20-30 HP (crank) from the cams, meaning approx 14-24HP at the wheels (assuming 80% driveline efficiency). I hope to dyno the car on the next few months. The sad part is I can't use the same dyno since the garage went out of business since last October.

And BTW, here's a clip of my car with the same exhaust setup, but WITH the DMC-CA cams...for those that do like the sound).

http://www.youtube.com/watch?v=2Ju1ueq3su4

[1batt4u]

Dmc-ca??

ok, http://www.dmccalifornia.com/ got it!

How hard or easy was it to change the cams??

[DeloreanJoshQ]

Dmc-ca??

ok, http://www.dmccalifornia.com/ got it!

How hard or easy was it to change the cams??

I've done it. If you are capable of removing the cylinder heads and re-aligning the timing chain setup then it is a piece of cake. Also, I would recommend upgrading the valve springs along with anything else that doesn't look good while taking it apart/putting it back together.....
Otherwise, get help....

[ramblinmike]

Also, I would recommend upgrading the valve springs

What is the update for the valve springs? Didn't know one existed.

[tyb323]

Justin, who's your videographer? He's pretty awesome. And that is a b-e-a-utiful Jeep TJ there!

[sdg3205]

Justin's car has a lot of burble. It sounds great. Does anyone with a DMC Stage 1 have similar burble? I've noticed since getting my Lambda system in tune and leaning out the car with the stock set-up I have burble. I can't hear it NEARLY as loud of course, but it's there.

[DMC3165]

I haven't yet gotten my car dyno'd "post cams", but I had 130 HP at the wheels on stock engine with the Hervey performance CAT & the Flowmaster Series 80 (stock exhaust manifolds & crossover pipe). While I find that hard to believe from just an exhaust system, Josh Q. found out that the same setup, but with stock muffler produced little-to-no power. The CAT is restrictive & the muffler is HIGHLY restrictive.

The cams made a big difference, but I won't claim 190 HP (crank) until I install headers & back it up with a dyno. For now (pre-header), my butt-dyno estimates I probably picked up 20-30 HP (crank) from the cams, meaning approx 14-24HP at the wheels (assuming 80% driveline efficiency). I hope to dyno the car on the next few months. The sad part is I can't use the same dyno since the garage went out of business since last October.

And BTW, here's a clip of my car with the same exhaust setup, but WITH the DMC-CA cams...for those that do like the sound).

http://www.youtube.com/watch?v=2Ju1ueq3su4

Damn! Sorry Justin I must have gotten it confused with something else. Could've sworn those were the HP #'s we were talking about.

[Grover]

What is the update for the valve springs? Didn't know one existed.

I too am interested.

[Farrar]

Does anyone with a DMC Stage 1 have similar burble?

Yep. My car has always burbled, even before I converted the fuel system in 2008. It had Stage I installed in, if memory serves, 2004 when it first came out as an exhaust-only option. (The exhaust is now rusting :( which I think is why Houston's new Stage I is all-stainless now.)

I will see if I can get some video/sound for you on a not-so-windy day.

Farrar

[DeloreanJoshQ]

I too am interested.

Mine are Comp Cams valve springs. When I took the heads to the machine shop and gave them the cam specs, they recommended upgrading the springs. They ordered and installed them, so I do not know the part number. However, if you call Comp Cams with the current spring and cam specs and then tell them the upgrade cam lift they will set you up with a set. However, IIRC, I was charged for 16 because they didnt' have them in a set of 12....

HTH...

[opethmike]

Wait a sec.... you actually have the specs for your cams? I've been trying to find out the specs of the various grinds the different vendors sell, and its been like squeezing blood from a stone.

[Farrar]

I was charged for 16 because they didnt' have them in a set of 12....

Or your mechanic has a 4-banger in need of new valve springs. ;)

Just kidding, of course!

Farrar

[TTait]

Dmc-ca??

ok, http://www.dmccalifornia.com/ got it!

How hard or easy was it to change the cams??

Its a bit easier with this:

http://cgi.ebay.com/ebaymotors/VOLVO-DELOREAN-RENAULT-PRV-B27-B28-FACTORY-TOOL-9995105-_W0QQcmdZViewItemQQhashZitem19c7869669QQitemZ11072 1668713QQptZMotorsQ5fAutomotiveQ5fTools

If your serious I'd buy the part on ebay, use it to do the job, then sell it again on ebay. Whats the worst that can happen, you take a $30 hit when you sell it?

This tool, used properly, means you don't have to re-time the engine chains. It holds the cam sprocket in position while you remove the heads, swap the cams, change out the head gasket, and reinstall. Then you repeat on the other side. I did it that way with a DIY bracket that almost worked well, but in the end I got worried the chain may have gone slack, so I ended up pulling off the rear fascia, muffler, timing chain cover etc to re-time, then had to reassemble it all.

Get the tool. Read the how to's carefully, and go for it. With chain timing out of the picture, your next toughest tasks are knowing not to lift the heads out, but roll them out. If I ever do it again I'll do it with this tool.

Even better plan now that I think of it - buy the tool, keep it, then when I need one you'll feel so indebted to me for this post that you'll lend it to me! Good luck!

PS - I like the cams

[sean]

Its a bit easier with this:

http://cgi.ebay.com/ebaymotors/VOLVO-DELOREAN-RENAULT-PRV-B27-B28-FACTORY-TOOL-9995105-_W0QQcmdZViewItemQQhashZitem19c7869669QQitemZ11072 1668713QQptZMotorsQ5fAutomotiveQ5fTools


Problem is that this tool only helps if you have the other tool that keeps tension on he chain while you remove the head. This tool just holds the sprocket in place while the head is out you still need the other tool so the chains don't slacken.

[TTait]

I didn't picture that. If the sprocket never moves, and the chain goes around the sprocket, why does the chain go slack? What does the other tool do and how is it used?

[sean]

I didn't picture that. If the sprocket never moves, and the chain goes around the sprocket, why does the chain go slack? What does the other tool do and how is it used?

Well, what holds the sprocket up? There is a bolt that goes through the sprocket and attaches to the cam shaft. In order to remove the head, which holds the cam shaft, you need to remove the bolt and back the sprocket off of the cam shaft. This is where slack can happen. The other tool I'm talking about mounts to the front timing cover and holds the sprocket and chain up, keeping tension, while you remove the head. Then you use the tool you listed if you need to rotate the engine while the head is out.

[TTait]

Oops - I have never had the tools, and I mistook this for the one that attaches to the timing chain cover. I never knew this one even existed.

Thanks for the correction. Hey - ignore what I said guys - get the other tool when it comes up on ebay instead.



Tom

[sean]

- get the other tool when it comes up on ebay instead.


It does pop up every now and then and usually the seller is asking around $100.

[TTait]

If you want to replace the cams, a good procedure is here:

http://www.dmcnews.com/Techsection/cylinderhead/headremovereplace.html

It got me through the job. Note however that the new cams will come with new valve clearances.