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2.0t HPFP swap on 1.8t

crxgator

Autocross Champion
Location
Raleigh, NC
Car(s)
All the MQBs
I have no experience apparently.
 

ClancyMcCintock

New member
Location
Tahoe
Car(s)
‘19 Alltrack, 84 GTi
I have no experience apparently.
Sorry. I didn’t mean that.

It’s just that I need a solution that plays nicely with the stock tune so I can pass emissions.
I thought if I could swap the internals on the stock HPFP, then any tune would work with it.
 
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ZuMBLe

Autocross Champion
Location
NY
Car(s)
Alltrack 6MT
You can flash back to stock and MPI will just turn off. You flash MPI tune back on and MPI works again.

Another win for MPI.
 

ClancyMcCintock

New member
Location
Tahoe
Car(s)
‘19 Alltrack, 84 GTi
Something I realized last night that seems like it should be added to the knowledge base, if it turns out to be “knowledge“ in practice:

The HPFP is run by the intake camshaft and spins in step with the engine, so it’s limitation is how much fuel it can put into the cylinders per rotation, which means it’s limitation is how much torque can be made, not power. How much fuel you can burn per rotation is torque. How much you can burn per minute is power.

402 hp is made by 325 ft.lbs of torque at 6500 rpm. Which is 25 psi of boost according to the Borg Warner matchbot.
That seems doable.

IE says it can get 364 ft.lbs of torque from the 1.8t, APR says 337, on 93 octane.

And since HP = Ft.lbs X RPM/5252, those two torques translate to 450hp and 417hp at 6500 rpm, respectively. Not that I believe the IE numbers. Just pointing out that 325 torques and 400 horsepowers seem reasonable.

This is all in theory, and I have no practical experience with it, but if it works out in practice, the hpfp wouldn’t be the limiting factor for power in the 1.8t. Until it is.

I should check my “pushing it” logs to see if my fuel pressures are dropping at 4000 rpm the same as they are at 6000 rpm.
 

aaronc7

Autocross Champion
Location
USA
Car(s)
17 S3
Here's the APR is20 file... they really lower the DI rail pressure in the lower rpm range in order to not overtax the stock 1.8 hpfp. The downsides of this are inferior fuel spray atomization and longer injector pulsewidth required (1.8 also has smaller injectors vs 2.0). It seems to work out fine, but certainly a 2.0 hpfp and "full" 200 bar rail pressure would be preferred/better.

1707066345255.png
 

ClancyMcCintock

New member
Location
Tahoe
Car(s)
‘19 Alltrack, 84 GTi
The best I can find from my logs with my modifiEd Maestro tune (I never touched fuel pressures) is 340 ftlbs at 2972 PUT at 4600 RPM and the rail pressure is 200000. So that’s not saying much. Except that Eurodyne is using full fuel pressure and APR is not, and the fuel pressure wasn’t dropping at that PUT and claimed torque.

I guess the question is, for people who have had they’re HPFP maxed out, do you see the rail pressure dropping at lower RPMs as much as at higher RPMs?
 
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crxgator

Autocross Champion
Location
Raleigh, NC
Car(s)
All the MQBs
The hpfp is a limiting factor. Here is a dyno of an is12, is20, and is20 with a gti hpfp (nothing else changed between the two is20 files).
 

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ClancyMcCintock

New member
Location
Tahoe
Car(s)
‘19 Alltrack, 84 GTi
The hpfp is a limiting factor. Here is a dyno of an is12, is20, and is20 with a gti hpfp (nothing else changed between the two is20 files).
Thank you for posting that dyno chart.

The lesson from it being that at 6500 the fuel pump is limiting the power. It doesn’t surprise me that the torque increases lower down, but it seems to defeat my idea of making 400 hp at 6500 rpm with 325 ftlbs.

The increased spool impresses me (I’m spool obsessed because I live at 6200 ft up and spool is a nightmare up here), but my limited knowledge of these things makes it so I don’t understand why. It’s fuel limited at lower boost levels?

Does the addition of MPI show similar changes?

When I search on Autotech HPFP on here I mostly get people trying to sell their used ones or unopened ones.
 
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MeltedSolid

Autocross Newbie
Location
San Francisco Bay Area
Car(s)
'15 Golf, e36 328i
I was sitting maxed out on the 1.8's HPFP for a while, the best I could get out of it was ~320-330 whp on 91, the limiting factor was HPFP in the mid range and injectors in the high range. Here is one of my logs from that time: https://datazap.me/u/meltedsolid/91-4th-gear-pull?log=0&data=2-17-25&solo=8-25-47&zoom=0-471
You can see the high pressure fuel rail pressure drop down to 137 bar, and if I tried to push it any harder it would start cutting out below 120 bar. At 5000rpm+, the injector pulse width is nearly maxed out, much higher and I would start clipping the exhaust stroke (don't really want to go above mid 7's at high rpm).
I've since gone MPI, upgraded the LPFP, and added a flex fuel sensor, and now have plenty of headroom running E85 at high 300's whp.

Also, I have a feeling the increased spool is false, and a trick of the dyno. That would require a change in the airflow, and would have nothing to do with fuel.
 

tigeo

Autocross Champion
I guess don't follow the HPFP thing. It's only "squirting" what volume you can get to it from the LPFP in the tank, if the LPFP is already pretty well at it's limit on the 1.8s wiht an IS38, how can the HPFP do much more?
 

MeltedSolid

Autocross Newbie
Location
San Francisco Bay Area
Car(s)
'15 Golf, e36 328i
I think with either MPI or a HPFP upgrade, a LPFP upgrade would be required/implied.
 

ClancyMcCintock

New member
Location
Tahoe
Car(s)
‘19 Alltrack, 84 GTi
I guess don't follow the HPFP thing. It's only "squirting" what volume you can get to it from the LPFP in the tank, if the LPFP is already pretty well at it's limit on the 1.8s wiht an IS38, how can the HPFP do much more?
It has the same LPFP as the GTi.
 

tigeo

Autocross Champion
It has the same LPFP as the GTi.
This is the hard-hitting info I come here for! Now it makes sense. I wonder why it seems to be hard to tune for/reliability issues with some of the kits etc. I read so much about? Oh, and 1.8 needs a different vacuum pump as well I believe?
 

ClancyMcCintock

New member
Location
Tahoe
Car(s)
‘19 Alltrack, 84 GTi
I was sitting maxed out on the 1.8's HPFP for a while, the best I could get out of it was ~320-330 whp on 91, the limiting factor was HPFP in the mid range and injectors in the high range. Here is one of my logs from that time: https://datazap.me/u/meltedsolid/91-4th-gear-pull?log=0&data=2-17-25&solo=8-25-47&zoom=0-471
You can see the high pressure fuel rail pressure drop down to 137 bar, and if I tried to push it any harder it would start cutting out below 120 bar. At 5000rpm+, the injector pulse width is nearly maxed out, much higher and I would start clipping the exhaust stroke (don't really want to go above mid 7's at high rpm).
I've since gone MPI, upgraded the LPFP, and added a flex fuel sensor, and now have plenty of headroom running E85 at high 300's whp.

Also, I have a feeling the increased spool is false, and a trick of the dyno. That would require a change in the airflow, and would have nothing to do with fuel.
Thank you for this. It’s very informative to me.

So torque (at lower RPMs) is limited by HPFP, and ultimate power is limited by the injectors. That’s of particular interest to me because I’m putting a Jetta GLi engine in which has the bigger injectors, but still Need things to work with the Alltrack ECU.

But I’m probably still going to do MPI, if I decide I can live with the terrible spool of having 200hp/liter at 6000‘ elevation. I might stick with 350hp for awhile though, see how it is. Maybe I’ll find a 420hp turbocharger that spools like an is20.:)
 

ClancyMcCintock

New member
Location
Tahoe
Car(s)
‘19 Alltrack, 84 GTi
This is the hard-hitting info I come here for! Now it makes sense. I wonder why it seems to be hard to tune for/reliability issues with some of the kits etc. I read so much about? Oh, and 1.8 needs a different vacuum pump as well I believe?
Are you being ironic? Sorry, I didn’t mean to offend.

I was just thinking of is38 OTS tunes like APR that get 400 hp on the GTi and 350 hp on the 1.8, both with the same LPFP, so I wasn’t thinking the LPFP was a limiting factor on the 350hp.

I’m not at all trying to be an expert. Please correct me / educate me if I’m wrong.
 
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