New Car 1980 Racecar 1500 Single 40 DCNF Dyno Sheet

B

Beauadams24

Low Mileage
Hello everyone. Getting this new to me X prepped for the 2024 season in the Southeast. I run with NASA but my Boxster LS swap project has taken a backseat so I can tinker with the FIAT. You might recognize the car as it was passed through a few Xweb members hands and ended up at Midwest Bayless for a while. I don't think Brayden was able to spend much time with the car before they sold it to a friend of mine who i acquired it from. I'm in constant contact with them but I wanted to post this up here for a discussion topic and give their burning ears a relief from my voice.

I added some photos of the details I was able to source about the build of the car. Note the megasquirt was removed for a stock intake manifold and a single 40DCNF. I'm looking for a few things from YOU; Does this dyno sheet look appropriate for the build of the engine? If not, what do you think may be wrong and where would you start? I almost wondered if the horsepower curve was mirrored BACKWARDS it looks so strange.

And in general I'd love to hear any words or wisdom you have for a racecar X owner while I wait for a rebuilt transmission to arrive.

Thanks!
Beau Adams
 

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I will take the first stab here. For a 40/80 cam profile, decked, and other goodies which are supposedly in the car then this is not normal. If anything, this looks like one of a couple potential items. 1. Timing advance is not working 2. Timing is just wrong 3. The cam is stock, not 40/80 or 4. the cam and head are stock, and finally you have a fuel supply issue and are running lean.

I just re-read some of the items. Is the lambda sensor still in the exhaust by chance? Might be worth hooking up an O2 sensor to see how rich/lean you are.

For timing, when the car is running, don't be surprised to have an obscene level of advance on the car. I remember some people saying they would have their setup with 0 degrees advanced to start and then immediately move to 20 degrees and progresses up past 40 degrees at full boogie. Speaking of timing, check it. Make sure the belt did not skip a tooth or two.

Boroscope would help determine the pistons as well.

Sorry I don't have a smoking gun for you on this. Just noticed your location, there are some good Fiat people in Georgia. Hopefully we have someone close by who can give you a second set of eyes on this.
 
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The only history I know is what Johnfiat told me. According to John, he bought the X new and eventually built up the car to race with his son. I don't know exactly when, but he sent the engine off to a local engine builder for some work. Unfortunately the engine builder passed away before completing the job. John put it back together, but said the car never ran very well after that. At some point John switched to racing a DSR car and the X sat for many years.

I bought the car in 2020 as a non-runner. Then it sat in my garage for at least a year before I had the chance to take it to MWB for an evaluation on what it would take to get it running again. The quote came back at a higher dollar amount than I was willing to put into the car, so Brayden bought the raceX. This was in late 2021 or early 2022.

The 1980 cars were rated at about 75HP to the crank with a 1500/FI setup, so 78HP to the wheels is an improvement. So, you have that going for you. :)
 
Hello Beau,
It looks like you have a good start. Your engine needs work, I would start with an evaluation (visual and leak down). Do a careful teardown checking clearances, etc. Build it back up carefully and take care to get the cam timing right. Depending on the tracks you run on you might advance the cam a few degrees when everything goes back together. Test the valve springs, if you have stock springs upgrade them.
My guess is that you have an FI dist. with the stock ICM. If so you might consider upgrading the ICM to enable higher RPM (MSD?). A good place to start with your ignition timing is 10' initial, 36' total. If you dyno it you may find some more power at 38' total?
9" wide wheels? Will the class you compete in allow 9" wide wheels? Those are pretty wide. What tires will you use?
Does the car have a rear swaybar? If so, remove it and sell it.
 
Beauadams24 said:
or a stock intake manifold
Click to expand...
Which one - it matters. Here is some stuff on topic from Steve C.

Euro /UK / Australian Specification X19 1500 (1980 casting) 4425193 128BS.2C.0, this manifold has runners that are 28mm at the face and are 28.5mm just inside. This is the manifold number Al Consetino mentions in his book, in a dyno / engine build sheet as being the "preferred" stock manifold.

Australian Specification X19 1300 (1978) manifold 4269347 128ASOC0025, this manifold has runners that are 26mm at the face, but just in they are 27mm

US spec 1300 (1974) manifold is Fiat part number 4320518, which is basically the same dimensions as the Australian spec 1300 manifold, but Australian spec ones have a vacuum takeoff point to power a fast idle device (goes where a brake booster hose would fit on something like a 128)

US spec 1300 (75-78) is part number 4401817

US spec 1500 (79 -80) is part number 4409482 (which looks just like the 1300 Australian spec manifold with the vacuum takeoff fitting but I've never had one in the flesh to measure or flow test)

Part numbers in a parts catalogue are usually different (often by just one number - like the 74USA manifold has a number in the book of 4320517, but the cast in number is 4320518 ) to what's cast into a part, as the cast in number is for the plain casting, but the book part number includes other fittings like studs etc ... for ease of identification most people use the cast in numbers to identify them.
Full thread https://xwebforums.com/forum/index.php?threads/carburetor-recommendation.44596/page-2#post-431967
 
Steve Thomas said:
probably limiting. Twin is the goto even on street
Click to expand...
A single DCNF can be tuned to give at least 90% of the peak HP that you would get with duals... remember with dual carbs you have an individual runner and each cylinder draws from just one carb throat ... with a single 2 throat carb and a plenum, each cylinder is drawing from both throats of the carb... with a single carb you miss out on the I.R benefits of being able to tune for wave reflection, but a single carb and plenum setup if done right can still give great results.

The reason for a single carb could be the racing rules he's working under... the rules may not allow dual carbs, and may even restrict him to the use of the original manifolding, and an adaptor plate... in which case the DCNF is probably mounted "sideways" and is far from ideal in terms of mixture distribution and airflow... being a racecar he's probably not worried about idle fuel distribution, but with a sideways DCNF thats definitely an issue as both idle mixture screws are positioned to one "side" of the engine...

Ideally the DCNF should be mounted "in line" with the crank, as this provided far superior idle mixture and general airflow and mixture distribution

DCNF's (as discussed in previous threads) can benefit a lot from the use of a bellmouth.

Low power output can be so many things ... and the OP has provided almost no detail about the engine to make any sort of assessment. The rules may require the use of standard valve sizes. Cylinder head prep is king when it comes to making power... adding cam/carb and exhaust can only do so much if there isnt enough flow thru the head, that's usually the bottleneck.

SteveC
 
I think what all the feedback adds up to is - you are going to have to pull the motor down to see what it actually is [CR, porting etc] before you can get any feel for what power it "should" be.
 
Beau:
The dyno sheet (is that flywheel or rear wheel?) is hard to read what rpm the peak is.
As Mike mentioned, you will have to do some investigating and find out exactly what is inside that engine. Are they parts and specs that work well with each other?
The first X race car I bought blew a head gasket at the end of a race. I took it apart and found it was a mix and match combination of used 1300 and 1500 parts (probably thrown together in a hurry at midnight Friday night.
I did some research and was advised what was needed to build an engine suitable for my race needs. I built a 1500cc X engine for SCCA H Production road racing and rear wheel dyno horsepower peak was 101 hp at 7000 rpm. The engine was 10.9:1 (via a decked block) compression, with euro spec 86.8 Borgo pistons, 11.3mm lift billet camshaft and a modified 32 DATRA (with stock 32mm throttle plates) carburetor. That day at the dyno, we also tested a stock 34 DMTR (25/26) and it made 100hp at the same rpm. Intake manifold was 4320518 casting number.
Dr.Jeff said:
I'm curious what you guys are expecting the dyno sheet to read for a engine like this?
Click to expand...
I expect 67 horsepower from a stock engine in good tune. It is possible to go up or down from there. My experience is with the stock single carb, & stock valve sizes and rods.
For a track day/race engine, a proper match of compression, camshaft, electronic ignition, header/tailpipe in a 1300 should get you 90hp at the rear wheels.
For a 1500, a proper match should get you to 100 rear wheel horsepower.
 

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If the car was previously running Megasquirt, there is a fair chance the mechanical advance was locked and the Megasquirt was controlling the advance curve. Before you pull apart the motor it might be worth pulling apart the distributor to see if anything has been done to lock the advance weights/mechanism. It will be a lot easier to pull apart the distributor than to pull apart the engine.
You could also check without disassembling anything. Use a timing light and see if the ignition advances with the engine just free revving. It should increase up to about 3-3.5K and then top out.

Dishy
 
The original poster added in his picture description the previous owners sale description which reads... ' Megasquirt fuel injection computer with all the parts to do ignition" which implies to me that the megasquirt wasn't involved with the ignition side of things.

Plus the dyno sheets are 4k thru to 8k... so all at what would be at full advance anyway... I'm pretty sure anyone running the car up on a dyno after replacing the manifold and carb would have set or at least checked the ignition timing, as that's basic tuning stuff.

SteveC
 
Scoped the cylinders last night and they appear to be stock pistons. Brayden concurs. Unfortunately the bottom end does not appear to be as advertised, not high compression pistons. Certainly explains the low compression numbers and lackluster dyno results. But that does mean there's room for improvement! Which is better than trying to find something broken/wrong!
 

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The write up you posted says " decked block with higher compression pistons"

Stock piston for a 1500 (non interference) on the left ... 1300 euro piston (interference) on the right ... that's "higher compression" than stock.

piston sohc flycut comparison.jpg



SteveC
 
Rupunzell said:
135psi -vs- 158psi.. check this.

More important by far, the chassis. Does this exxe have the PBS "lower the body around the suspension" alterations?
It does have the PBS style "roll cage" which is IMO, not safe at all in a real world roll over on track.

Bernice
Click to expand...
I agree on the chassis. My car has the suspension adjustments, and they are terrible. I am probably going to put mine back to normal.

You have quite the interesting build going on. I would just create a list and start from the top and see where you end up. Timing, fuel pressure, jet sizing, venturi size, etc. Then after we get that info, as Bernice said the PSI difference needs to be reviewed. Might be worth while to remove the head anways and refresh the gasket, true up the head, put a guage on the piston to see what the level of pop out on the piston is, if any.
 
With careful block decking/head milling/head gasket selection you can get up to 11:1 compression - even with flat top pistons.
To your low compression numbers - I would start diagnosing that by confirming cam timing. Bad cam timing will cause the compression issues that you're seeing. And if I remember correctly, the PO (who built the engine?) admitted that he thought the cam timing was not performed correctly.
My advice is to tear the engine down to confirm everything is right. But before you do take some time to see what you have. It's no fun breaking your engine at the track and ruining your weekend. And, while it takes some time and money to tear it down now, it will be a lot worse later if it breaks at the track.
But no matter what you do - be prepared to be under powered at the track. You will be.
 
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